1POSTCONF(5) File Formats Manual POSTCONF(5)
2
6 postconf - Postfix configuration parameters
7
9 postconf parameter ...
10 postconf -e "parameter=value" ...
12
14 The Postfix main.cf configuration file specifies parameters that con‐
15 trol the operation of the Postfix mail system. Typically the file con‐
16 tains only a small subset of all parameters; parameters not specified
17 are left at their default values.
18 The general format of the main.cf file is as follows:
20 • Each logical line has the form "parameter = value". Whitespace
22 around the "=" is ignored, as is whitespace at the end of a log‐
23 ical line.
24 • Empty lines and whitespace-only lines are ignored, as are lines
26 whose first non-whitespace character is a `#'.
27 • A logical line starts with non-whitespace text. A line that
29 starts with whitespace continues a logical line.
30 • A parameter value may refer to other parameters.
32 • The expressions "$name" and "${name}" are recursively re‐
34 placed with the value of the named parameter. The parame‐
35 ter name must contain only characters from the set [a-zA-
36 Z0-9_]. An undefined parameter value is replaced with the
37 empty value.
38 • The expressions "${name?value}" and "${name?{value}}" are
40 replaced with "value" when "$name" is non-empty. The pa‐
41 rameter name must contain only characters from the set
42 [a-zA-Z0-9_]. These forms are supported with Postfix ver‐
43 sions >= 2.2 and >= 3.0, respectively.
44 • The expressions "${name:value}" and "${name:{value}}" are
46 replaced with "value" when "$name" is empty. The parame‐
47 ter name must contain only characters from the set [a-zA-
48 Z0-9_]. These forms are supported with Postfix versions
49 >= 2.2 and >= 3.0, respectively.
50 • The expression "${name?{value1}:{value2}}" is replaced
52 with "value1" when "$name" is non-empty, and with
53 "value2" when "$name" is empty. The "{}" is required for
54 "value1", optional for "value2". The parameter name must
55 contain only characters from the set [a-zA-Z0-9_]. This
56 form is supported with Postfix versions >= 3.0.
57 • The first item inside "${...}" may be a relational ex‐
59 pression of the form: "{value3} == {value4}". Besides the
60 "==" (equality) operator Postfix supports "!=" (inequal‐
61 ity), "<", "<=", ">=", and ">". The comparison is numeri‐
62 cal when both operands are all digits, otherwise the com‐
63 parison is lexicographical. These forms are supported
64 with Postfix versions >= 3.0.
65 • Each "value" is subject to recursive named parameter and
67 relational expression evaluation, except where noted.
68 • Whitespace before or after each "{value}" is ignored.
70 • Specify "$$" to produce a single "$" character.
72 • The legacy form "$(...)" is equivalent to the preferred
74 form "${...}".
75 • When the same parameter is defined multiple times, only the last
77 instance is remembered.
78 • Otherwise, the order of main.cf parameter definitions does not
80 matter.
81 The remainder of this document is a description of all Postfix configu‐
83 ration parameters. Default values are shown after the parameter name in
84 parentheses, and can be looked up with the "postconf -d" command.
85 Note: this is not an invitation to make changes to Postfix configura‐
87 tion parameters. Unnecessary changes can impair the operation of the
88 mail system.
89
91 The recipient of undeliverable mail that cannot be returned to the
92 sender. This feature is enabled with the notify_classes parameter.
93
95 The numerical Postfix SMTP server response code for an access(5) map
96 "defer" action, including "defer_if_permit" or "defer_if_reject". Prior
97 to Postfix 2.6, the response is hard-coded as "450".
98 Do not change this unless you have a complete understanding of RFC
100 5321.
101 This feature is available in Postfix 2.6 and later.
103
105 The numerical Postfix SMTP server response code for an access(5) map
106 "reject" action.
107 Do not change this unless you have a complete understanding of RFC
109 5321.
110
112 The amount of time between verify(8) address verification database
113 cleanup runs. This feature requires that the database supports the
114 "delete" and "sequence" operators. Specify a zero interval to disable
115 database cleanup.
116 After each database cleanup run, the verify(8) daemon logs the number
118 of entries that were retained and dropped. A cleanup run is logged as
119 "partial" when the daemon terminates early after "postfix reload",
120 "postfix stop", or no requests for $max_idle seconds.
121 Time units: s (seconds), m (minutes), h (hours), d (days), w (weeks).
123 This feature is available in Postfix 2.7.
125
127 Overrides the default_transport parameter setting for address verifica‐
128 tion probes.
129 This feature is available in Postfix 2.1 and later.
131
133 Overrides the local_transport parameter setting for address verifica‐
134 tion probes.
135 This feature is available in Postfix 2.1 and later.
137
139 Lookup table for persistent address verification status storage. The
140 table is maintained by the verify(8) service, and is opened before the
141 process releases privileges.
142 The lookup table is persistent by default (Postfix 2.7 and later).
144 Specify an empty table name to keep the information in volatile memory
145 which is lost after "postfix reload" or "postfix stop". This is the de‐
146 fault with Postfix version 2.6 and earlier.
147 Specify a location in a file system that will not fill up. If the data‐
149 base becomes corrupted, the world comes to an end. To recover delete
150 (NOT: truncate) the file and do "postfix reload".
151 Postfix daemon processes do not use root privileges when opening this
153 file (Postfix 2.5 and later). The file must therefore be stored under
154 a Postfix-owned directory such as the data_directory. As a migration
155 aid, an attempt to open the file under a non-Postfix directory is redi‐
156 rected to the Postfix-owned data_directory, and a warning is logged.
157 Examples:
159 address_verify_map = hash:/var/lib/postfix/verify
161 address_verify_map = btree:/var/lib/postfix/verify
162 This feature is available in Postfix 2.1 and later.
164
166 Enable caching of failed address verification probe results. When this
167 feature is enabled, the cache may pollute quickly with garbage. When
168 this feature is disabled, Postfix will generate an address probe for
169 every lookup.
170 This feature is available in Postfix 2.1 and later.
172
174 The time after which a failed probe expires from the address verifica‐
175 tion cache.
176 Time units: s (seconds), m (minutes), h (hours), d (days), w (weeks).
178 This feature is available in Postfix 2.1 and later.
180
182 The time after which a failed address verification probe needs to be
183 refreshed.
184 Time units: s (seconds), m (minutes), h (hours), d (days), w (weeks).
186 This feature is available in Postfix 2.1 and later.
188
190 A safety limit that prevents address verification requests from over‐
191 whelming the Postfix queue. By default, the number of pending requests
192 is limited to 1/4 of the active queue maximum size (qmgr_message_ac‐
193 tive_limit). The queue manager enforces the limit by tempfailing re‐
194 quests that exceed the limit. This affects only unknown addresses and
195 inactive addresses that have expired, because the verify(8) daemon au‐
196 tomatically refreshes an active address before it expires.
197 This feature is available in Postfix 3.1 and later.
199
201 How many times to query the verify(8) service for the completion of an
202 address verification request in progress.
203 By default, the Postfix SMTP server polls the verify(8) service up to
205 three times under non-overload conditions, and only once when under
206 overload. With Postfix version 2.5 and earlier, the SMTP server always
207 polls the verify(8) service up to three times by default.
208 Specify 1 to implement a crude form of greylisting, that is, always de‐
210 fer the first delivery request for a new address.
211 Examples:
213 # Postfix <= 2.6 default
215 address_verify_poll_count = 3
216 # Poor man's greylisting
217 address_verify_poll_count = 1
218 This feature is available in Postfix 2.1 and later.
220
222 The delay between queries for the completion of an address verification
223 request in progress.
224 The default polling delay is 3 seconds.
226 Time units: s (seconds), m (minutes), h (hours), d (days), w (weeks).
228 This feature is available in Postfix 2.1 and later.
230
232 The time after which a successful probe expires from the address veri‐
233 fication cache.
234 Time units: s (seconds), m (minutes), h (hours), d (days), w (weeks).
236 This feature is available in Postfix 2.1 and later.
238
240 The time after which a successful address verification probe needs to
241 be refreshed. The address verification status is not updated when the
242 probe fails (optimistic caching).
243 Time units: s (seconds), m (minutes), h (hours), d (days), w (weeks).
245 This feature is available in Postfix 2.1 and later.
247
249 Overrides the relay_transport parameter setting for address verifica‐
250 tion probes.
251 This feature is available in Postfix 2.1 and later.
253
255 Overrides the relayhost parameter setting for address verification
256 probes. This information can be overruled with the transport(5) table.
257 This feature is available in Postfix 2.1 and later.
259
261 The sender address to use in address verification probes; prior to
262 Postfix 2.5 the default was "postmaster". To avoid problems with ad‐
263 dress probes that are sent in response to address probes, the Postfix
264 SMTP server excludes the probe sender address from all SMTPD access
265 blocks.
266 Specify an empty value (address_verify_sender =) or <> if you want to
268 use the null sender address. Beware, some sites reject mail from <>,
269 even though RFCs require that such addresses be accepted.
270 Examples:
272 address_verify_sender = <>
274 address_verify_sender = postmaster@my.domain
275 This feature is available in Postfix 2.1 and later.
277
279 pendent_default_transport_maps)
280 Overrides the sender_dependent_default_transport_maps parameter setting
281 for address verification probes.
282 This feature is available in Postfix 2.7 and later.
284
286 layhost_maps)
287 Overrides the sender_dependent_relayhost_maps parameter setting for ad‐
288 dress verification probes.
289 This feature is available in Postfix 2.3 and later.
291
293 The time between changes in the time-dependent portion of address veri‐
294 fication probe sender addresses. The time-dependent portion is appended
295 to the localpart of the address specified with the address_ver‐
296 ify_sender parameter. This feature is ignored when the probe sender ad‐
297 dresses is the null sender, i.e. the address_verify_sender value is
298 empty or <>.
299 Historically, the probe sender address was fixed. This has caused such
301 addresses to end up on spammer mailing lists, and has resulted in
302 wasted network and processing resources.
303 To enable time-dependent probe sender addresses, specify a non-zero
305 time value (an integral value plus an optional one-letter suffix that
306 specifies the time unit). Specify a value of at least several hours,
307 to avoid problems with senders that use greylisting. Avoid nice TTL
308 values, to make the result less predictable. Time units are: s (sec‐
309 onds), m (minutes), h (hours), d (days), w (weeks).
310 This feature is available in Postfix 2.9 and later.
312
314 The name of the verify(8) address verification service. This service
315 maintains the status of sender and/or recipient address verification
316 probes, and generates probes on request by other Postfix processes.
317
319 Overrides the transport_maps parameter setting for address verification
320 probes.
321 This feature is available in Postfix 2.1 and later.
323
325 Overrides the virtual_transport parameter setting for address verifica‐
326 tion probes.
327 This feature is available in Postfix 2.1 and later.
329
331 The alias databases for local(8) delivery that are updated with
332 "newaliases" or with "sendmail -bi".
333 This is a separate configuration parameter because not all the tables
335 specified with $alias_maps have to be local files.
336 Examples:
338 alias_database = hash:/etc/aliases
340 alias_database = hash:/etc/mail/aliases
341
343 The alias databases that are used for local(8) delivery. See aliases(5)
344 for syntax details. Specify zero or more "type:name" lookup tables,
345 separated by whitespace or comma. Tables will be searched in the speci‐
346 fied order until a match is found. Note: these lookups are recursive.
347 The default list is system dependent. On systems with NIS, the default
349 is to search the local alias database, then the NIS alias database.
350 If you change the alias database, run "postalias /etc/aliases" (or
352 wherever your system stores the mail alias file), or simply run
353 "newaliases" to build the necessary DBM or DB file.
354 The local(8) delivery agent disallows regular expression substitution
356 of $1 etc. in alias_maps, because that would open a security hole.
357 The local(8) delivery agent will silently ignore requests to use the
359 proxymap(8) server within alias_maps. Instead it will open the table
360 directly. Before Postfix version 2.2, the local(8) delivery agent will
361 terminate with a fatal error.
362 Examples:
364 alias_maps = hash:/etc/aliases, nis:mail.aliases
366 alias_maps = hash:/etc/aliases
367
369 Restrict local(8) mail delivery to external commands. The default is
370 to disallow delivery to "|command" in :include: files (see aliases(5)
371 for the text that defines this terminology).
372 Specify zero or more of: alias, forward or include, in order to allow
374 commands in aliases(5), .forward files or in :include: files, respec‐
375 tively.
376 Example:
378 allow_mail_to_commands = alias,forward,include
380
382 Restrict local(8) mail delivery to external files. The default is to
383 disallow "/file/name" destinations in :include: files (see aliases(5)
384 for the text that defines this terminology).
385 Specify zero or more of: alias, forward or include, in order to allow
387 "/file/name" destinations in aliases(5), .forward files and in :in‐
388 clude: files, respectively.
389 Example:
391 allow_mail_to_files = alias,forward,include
393
395 Allow a sender or recipient address to have `-' as the first character.
396 By default, this is not allowed, to avoid accidents with software that
397 passes email addresses via the command line. Such software would not be
398 able to distinguish a malicious address from a bona fide command-line
399 option. Although this can be prevented by inserting a "--" option ter‐
400 minator into the command line, this is difficult to enforce consis‐
401 tently and globally.
402 As of Postfix version 2.5, this feature is implemented by trivial-re‐
404 write(8). With earlier versions this feature was implemented by
405 qmgr(8) and was limited to recipient addresses only.
406
408 Enable the rewriting of the form "user%domain" to "user@domain". This
409 is enabled by default.
410 Note: as of Postfix version 2.2, message header address rewriting hap‐
412 pens only when one of the following conditions is true:
413 • The message is received with the Postfix sendmail(1) command,
415 • The message is received from a network client that matches $lo‐
417 cal_header_rewrite_clients,
418 • The message is received from the network, and the re‐
420 mote_header_rewrite_domain parameter specifies a non-empty
421 value.
422 To get the behavior before Postfix version 2.2, specify "lo‐
424 cal_header_rewrite_clients = static:all".
425 Example:
427 allow_percent_hack = no
429
431 Forward mail with sender-specified routing (user[@%!]remote[@%!]site)
432 from untrusted clients to destinations matching $relay_domains.
433 By default, this feature is turned off. This closes a nasty open relay
435 loophole where a backup MX host can be tricked into forwarding junk
436 mail to a primary MX host which then spams it out to the world.
437 This parameter also controls if non-local addresses with sender-speci‐
439 fied routing can match Postfix access tables. By default, such ad‐
440 dresses cannot match Postfix access tables, because the address is am‐
441 biguous.
442
444 A list of non-default Postfix configuration directories that may be
445 specified with "-c config_directory" on the command line (in the case
446 of sendmail(1), with the "-C" option), or via the MAIL_CONFIG environ‐
447 ment parameter.
448 This list must be specified in the default Postfix main.cf file, and
450 will be used by set-gid Postfix commands such as postqueue(1) and post‐
451 drop(1).
452 Specify absolute pathnames, separated by comma or space. Note: $name
454 expansion is not supported.
455
457 Always add (Resent-) From:, To:, Date: or Message-ID: headers when not
458 present. Postfix 2.6 and later add these headers only when clients
459 match the local_header_rewrite_clients parameter setting. Earlier
460 Postfix versions always add these headers; this may break DKIM signa‐
461 tures that cover non-existent headers. The undisclosed_recipi‐
462 ents_header parameter setting determines whether a To: header will be
463 added.
464
466 Optional address that receives a "blind carbon copy" of each message
467 that is received by the Postfix mail system.
468 Note: with Postfix 2.3 and later the BCC address is added as if it was
470 specified with NOTIFY=NONE. The sender will not be notified when the
471 BCC address is undeliverable, as long as all down-stream software im‐
472 plements RFC 3461.
473 Note: with Postfix 2.2 and earlier the sender will be notified when the
475 BCC address is undeliverable.
476 Note: automatic BCC recipients are produced only for new mail. To
478 avoid mailer loops, automatic BCC recipients are not generated after
479 Postfix forwards mail internally, or after Postfix generates mail it‐
480 self.
481
483 The time unit over which client connection rates and other rates are
484 calculated.
485 This feature is implemented by the anvil(8) service which is available
487 in Postfix version 2.2 and later.
488 The default interval is relatively short. Because of the high frequency
490 of updates, the anvil(8) server uses volatile memory only. Thus, infor‐
491 mation is lost whenever the process terminates.
492 Time units: s (seconds), m (minutes), h (hours), d (days), w (weeks).
494 The default time unit is s (seconds).
495
497 How frequently the anvil(8) connection and rate limiting server logs
498 peak usage information.
499 This feature is available in Postfix 2.2 and later.
501 Time units: s (seconds), m (minutes), h (hours), d (days), w (weeks).
503 The default time unit is s (seconds).
504
506 With locally submitted mail, append the string "@$myorigin" to mail ad‐
507 dresses without domain information. With remotely submitted mail, ap‐
508 pend the string "@$remote_header_rewrite_domain" instead.
509 Note 1: this feature is enabled by default and must not be turned off.
511 Postfix does not support domain-less addresses.
512 Note 2: with Postfix version 2.2, message header address rewriting hap‐
514 pens only when one of the following conditions is true:
515 • The message is received with the Postfix sendmail(1) command,
517 • The message is received from a network client that matches $lo‐
519 cal_header_rewrite_clients,
520 • The message is received from the network, and the re‐
522 mote_header_rewrite_domain parameter specifies a non-empty
523 value.
524 To get the behavior before Postfix version 2.2, specify "lo‐
526 cal_header_rewrite_clients = static:all".
527
529 With locally submitted mail, append the string ".$mydomain" to ad‐
530 dresses that have no ".domain" information. With remotely submitted
531 mail, append the string ".$remote_header_rewrite_domain" instead.
532 Note 1: this feature is enabled by default. If disabled, users will not
534 be able to send mail to "user@partialdomainname" but will have to spec‐
535 ify full domain names instead.
536 Note 2: with Postfix version 2.2, message header address rewriting hap‐
538 pens only when one of the following conditions is true:
539 • The message is received with the Postfix sendmail(1) command,
541 • The message is received from a network client that matches $lo‐
543 cal_header_rewrite_clients,
544 • The message is received from the network, and the re‐
546 mote_header_rewrite_domain parameter specifies a non-empty
547 value.
548 To get the behavior before Postfix version 2.2, specify "lo‐
550 cal_header_rewrite_clients = static:all".
551
553 How long the postkick(1) command waits for a request to enter the Post‐
554 fix daemon process input buffer before giving up.
555 Time units: s (seconds), m (minutes), h (hours), d (days), w (weeks).
557 The default time unit is s (seconds).
558 This feature is available in Postfix 2.1 and later.
560
562 List of users who are authorized to flush the queue.
563 By default, all users are allowed to flush the queue. Access is always
565 granted if the invoking user is the super-user or the $mail_owner user.
566 Otherwise, the real UID of the process is looked up in the system pass‐
567 word file, and access is granted only if the corresponding login name
568 is on the access list. The username "unknown" is used for processes
569 whose real UID is not found in the password file.
570 Specify a list of user names, "/file/name" or "type:table" patterns,
572 separated by commas and/or whitespace. The list is matched left to
573 right, and the search stops on the first match. A "/file/name" pattern
574 is replaced by its contents; a "type:table" lookup table is matched
575 when a name matches a lookup key (the lookup result is ignored). Con‐
576 tinue long lines by starting the next line with whitespace. Specify
577 "!pattern" to exclude a name from the list. The form "!/file/name" is
578 supported only in Postfix version 2.4 and later.
579 This feature is available in Postfix 2.2 and later.
581
583 List of users who are authorized to view the queue.
584 By default, all users are allowed to view the queue. Access is always
586 granted if the invoking user is the super-user or the $mail_owner user.
587 Otherwise, the real UID of the process is looked up in the system pass‐
588 word file, and access is granted only if the corresponding login name
589 is on the access list. The username "unknown" is used for processes
590 whose real UID is not found in the password file.
591 Specify a list of user names, "/file/name" or "type:table" patterns,
593 separated by commas and/or whitespace. The list is matched left to
594 right, and the search stops on the first match. A "/file/name" pattern
595 is replaced by its contents; a "type:table" lookup table is matched
596 when a name matches a lookup key (the lookup result is ignored). Con‐
597 tinue long lines by starting the next line with whitespace. Specify
598 "!pattern" to exclude a user name from the list. The form "!/file/name"
599 is supported only in Postfix version 2.4 and later.
600 This feature is available in Postfix 2.2 and later.
602
604 List of users who are authorized to submit mail with the sendmail(1)
605 command (and with the privileged postdrop(1) helper command).
606 By default, all users are allowed to submit mail. Otherwise, the real
608 UID of the process is looked up in the system password file, and access
609 is granted only if the corresponding login name is on the access list.
610 The username "unknown" is used for processes whose real UID is not
611 found in the password file. To deny mail submission access to all users
612 specify an empty list.
613 Specify a list of user names, "/file/name" or "type:table" patterns,
615 separated by commas and/or whitespace. The list is matched left to
616 right, and the search stops on the first match. A "/file/name" pattern
617 is replaced by its contents; a "type:table" lookup table is matched
618 when a name matches a lookup key (the lookup result is ignored). Con‐
619 tinue long lines by starting the next line with whitespace. Specify
620 "!pattern" to exclude a user name from the list. The form "!/file/name"
621 is supported only in Postfix version 2.4 and later.
622 Example:
624 authorized_submit_users = !www, static:all
626 This feature is available in Postfix 2.2 and later.
628
630 What remote SMTP clients are allowed to specify the XVERP command.
631 This command requests that mail be delivered one recipient at a time
632 with a per recipient return address.
633 By default, only trusted clients are allowed to specify XVERP.
635 This parameter was introduced with Postfix version 1.1. Postfix ver‐
637 sion 2.1 renamed this parameter to smtpd_authorized_verp_clients and
638 changed the default to none.
639 Specify a list of network/netmask patterns, separated by commas and/or
641 whitespace. The mask specifies the number of bits in the network part
642 of a host address. You can also specify hostnames or .domain names (the
643 initial dot causes the domain to match any name below it),
644 "/file/name" or "type:table" patterns. A "/file/name" pattern is re‐
645 placed by its contents; a "type:table" lookup table is matched when a
646 table entry matches a lookup string (the lookup result is ignored).
647 Continue long lines by starting the next line with whitespace. Specify
648 "!pattern" to exclude an address or network block from the list. The
649 form "!/file/name" is supported only in Postfix version 2.4 and later.
650 Note: IP version 6 address information must be specified inside [] in
652 the authorized_verp_clients value, and in files specified with
653 "/file/name". IP version 6 addresses contain the ":" character, and
654 would otherwise be confused with a "type:table" pattern.
655
657 Produce additional bounce(8) logfile records that can be read by Post‐
658 fix versions before 2.0. The current and more extensible "name = value"
659 format is needed in order to implement more sophisticated functional‐
660 ity.
661 This feature is available in Postfix 2.1 and later.
663
665 The per-table I/O buffer size for programs that create Berkeley DB hash
666 or btree tables. Specify a byte count.
667 This feature is available in Postfix 2.0 and later.
669
671 The per-table I/O buffer size for programs that read Berkeley DB hash
672 or btree tables. Specify a byte count.
673 This feature is available in Postfix 2.0 and later.
675
677 Where the Postfix SMTP client should deliver mail when it detects a
678 "mail loops back to myself" error condition. This happens when the lo‐
679 cal MTA is the best SMTP mail exchanger for a destination not listed in
680 $mydestination, $inet_interfaces, $proxy_interfaces, $virtual_alias_do‐
681 mains, or $virtual_mailbox_domains. By default, the Postfix SMTP
682 client returns such mail as undeliverable.
683 Specify, for example, "best_mx_transport = local" to pass the mail from
685 the Postfix SMTP client to the local(8) delivery agent. You can specify
686 any message delivery "transport" or "transport:nexthop" that is defined
687 in the master.cf file. See the transport(5) manual page for the syntax
688 and meaning of "transport" or "transport:nexthop".
689 However, this feature is expensive because it ties up a Postfix SMTP
691 client process while the local(8) delivery agent is doing its work. It
692 is more efficient (for Postfix) to list all hosted domains in a table
693 or database.
694
696 Whether or not to use the local biff service. This service sends "new
697 mail" notifications to users who have requested new mail notification
698 with the UNIX command "biff y".
699 For compatibility reasons this feature is on by default. On systems
701 with lots of interactive users, the biff service can be a performance
702 drain. Specify "biff = no" in main.cf to disable.
703
705 Optional lookup tables for content inspection as specified in the
706 body_checks(5) manual page.
707 Note: with Postfix versions before 2.0, these rules inspect all content
709 after the primary message headers.
710
712 How much text in a message body segment (or attachment, if you prefer
713 to use that term) is subjected to body_checks inspection. The amount
714 of text is limited to avoid scanning huge attachments.
715 This feature is available in Postfix 2.0 and later.
717
719 The recipient of postmaster notifications with the message headers of
720 mail that Postfix did not deliver and of SMTP conversation transcripts
721 of mail that Postfix did not receive. This feature is enabled with the
722 notify_classes parameter.
723
725 Consider a bounce message as undeliverable, when delivery fails with a
726 temporary error, and the time in the queue has reached the
727 bounce_queue_lifetime limit. By default, this limit is the same as for
728 regular mail.
729 Time units: s (seconds), m (minutes), h (hours), d (days), w (weeks).
731 The default time unit is d (days).
732 Specify 0 when mail delivery should be tried only once.
734 This feature is available in Postfix 2.1 and later.
736
738 The name of the bounce(8) service. This service maintains a record of
739 failed delivery attempts and generates non-delivery notifications.
740 This feature is available in Postfix 2.0 and later.
742
744 The maximal amount of original message text that is sent in a non-de‐
745 livery notification. Specify a byte count. A message is returned as
746 either message/rfc822 (the complete original) or as text/rfc822-headers
747 (the headers only). With Postfix version 2.4 and earlier, a message is
748 always returned as message/rfc822 and is truncated when it exceeds the
749 size limit.
750 Notes:
752 • If you increase this limit, then you should increase the
754 mime_nesting_limit value proportionally.
755 • Be careful when making changes. Excessively large values will
757 result in the loss of non-delivery notifications, when a bounce
758 message size exceeds a local or remote MTA's message size limit.
759
761 Pathname of a configuration file with bounce message templates. These
762 override the built-in templates of delivery status notification (DSN)
763 messages for undeliverable mail, for delayed mail, successful delivery,
764 or delivery verification. The bounce(5) manual page describes how to
765 edit and test template files.
766 Template message body text may contain $name references to Postfix con‐
768 figuration parameters. The result of $name expansion can be previewed
769 with "postconf -b file_name" before the file is placed into the Postfix
770 configuration directory.
771 This feature is available in Postfix 2.3 and later.
773
775 Enable interoperability with remote SMTP clients that implement an ob‐
776 solete version of the AUTH command (RFC 4954). Examples of such clients
777 are MicroSoft Outlook Express version 4 and MicroSoft Exchange version
778 5.0.
779 Specify "broken_sasl_auth_clients = yes" to have Postfix advertise AUTH
781 support in a non-standard way.
782
784 header_sender, header_recipient)
785 What addresses are subject to canonical_maps address mapping. By de‐
786 fault, canonical_maps address mapping is applied to envelope sender and
787 recipient addresses, and to header sender and header recipient ad‐
788 dresses.
789 Specify one or more of: envelope_sender, envelope_recipient,
791 header_sender, header_recipient
792 This feature is available in Postfix 2.2 and later.
794
796 Optional address mapping lookup tables for message headers and en‐
797 velopes. The mapping is applied to both sender and recipient addresses,
798 in both envelopes and in headers, as controlled with the canoni‐
799 cal_classes parameter. This is typically used to clean up dirty ad‐
800 dresses from legacy mail systems, or to replace login names by First‐
801 name.Lastname. The table format and lookups are documented in canoni‐
802 cal(5). For an overview of Postfix address manipulations see the AD‐
803 DRESS_REWRITING_README document.
804 Specify zero or more "type:name" lookup tables, separated by whitespace
806 or comma. Tables will be searched in the specified order until a match
807 is found. Note: these lookups are recursive.
808 If you use this feature, run "postmap /etc/postfix/canonical" to build
810 the necessary DBM or DB file after every change. The changes will be‐
811 come visible after a minute or so. Use "postfix reload" to eliminate
812 the delay.
813 Note: with Postfix version 2.2, message header address mapping happens
815 only when message header address rewriting is enabled:
816 • The message is received with the Postfix sendmail(1) command,
818 • The message is received from a network client that matches $lo‐
820 cal_header_rewrite_clients,
821 • The message is received from the network, and the re‐
823 mote_header_rewrite_domain parameter specifies a non-empty
824 value.
825 To get the behavior before Postfix version 2.2, specify "lo‐
827 cal_header_rewrite_clients = static:all".
828 Examples:
830 canonical_maps = dbm:/etc/postfix/canonical
832 canonical_maps = hash:/etc/postfix/canonical
833
835 The name of the cleanup(8) service. This service rewrites addresses
836 into the standard form, and performs canonical(5) address mapping and
837 virtual(5) aliasing.
838 This feature is available in Postfix 2.0 and later.
840
842 The location of all postfix administrative commands.
843
845 The local(8) delivery agent working directory for delivery to external
846 command. Failure to change directory causes the delivery to be de‐
847 ferred.
848 The command_execution_directory value is not subject to Postfix config‐
850 uration parameter $name expansion. Instead, the following $name expan‐
851 sions are done on command_execution_directory before the directory is
852 used. Expansion happens in the context of the delivery request. The
853 result of $name expansion is filtered with the character set that is
854 specified with the execution_directory_expansion_filter parameter.
855 $user The recipient's username.
857 $shell The recipient's login shell pathname.
859 $home The recipient's home directory.
861 $recipient
863 The full recipient address.
864 $extension
866 The optional recipient address extension.
867 $domain
869 The recipient domain.
870 $local The entire recipient localpart.
872 $recipient_delimiter
874 The address extension delimiter that was found in the recipient
875 address (Postfix 2.11 and later), or the system-wide recipient
876 address extension delimiter (Postfix 2.10 and earlier).
877 ${name?value}
879 Expands to value when $name is non-empty.
880 ${name:value}
882 Expands to value when $name is empty.
883 Instead of $name you can also specify ${name} or $(name).
885 This feature is available in Postfix 2.2 and later.
887
889 Restrict the characters that the local(8) delivery agent allows in
890 $name expansions of $mailbox_command and $command_execution_directory.
891 Characters outside the allowed set are replaced by underscores.
892
894 Time limit for delivery to external commands. This limit is used by the
895 local(8) delivery agent, and is the default time limit for delivery by
896 the pipe(8) delivery agent.
897 Note: if you set this time limit to a large value you must update the
899 global ipc_timeout parameter as well.
900
902 A safety net that causes Postfix to run with backwards-compatible de‐
903 fault settings after an upgrade to a newer Postfix version.
904 With backwards compatibility turned on (the main.cf compatibility_level
906 value is less than the Postfix built-in value), Postfix looks for set‐
907 tings that are left at their implicit default value, and logs a message
908 when a backwards-compatible default setting is required.
909 using backwards-compatible default setting name=value
911 to [accept a specific client request]
912 using backwards-compatible default setting name=value
914 to [enable specific Postfix behavior]
915 See COMPATIBILITY_README for specific message details. If such a mes‐
917 sage is logged in the context of a legitimate request, the system ad‐
918 ministrator should make the backwards-compatible setting permanent in
919 main.cf or master.cf, for example:
920 # postconf name=value
922 # postfix reload
923 When no more backwards-compatible settings need to be made permanent,
925 the administrator should turn off backwards compatibility by updating
926 the compatibility_level setting in main.cf:
927 # postconf compatibility_level=N
929 # postfix reload
930 For N specify the number that is logged in your postfix(1) warning mes‐
932 sage:
933 warning: To disable backwards compatibility use "postconf
935 compatibility_level=N" and "postfix reload"
936 Starting with Postfix version 3.6, the compatibility level in the above
938 warning message is the Postfix version that introduced the last incom‐
939 patible change. The level is formatted as major.minor.patch, where
940 patch is usually omitted and defaults to zero. Earlier compatibility
941 levels are 0, 1 and 2.
942 NOTE: this also introduces support for the "<level", "<=level", and
944 other operators to compare compatibility levels. With the standard op‐
945 erators "<", "<=", etc., compatibility level "3.10" would be smaller
946 than "3.9" which is undesirable.
947 This feature is available in Postfix 3.0 and later.
949
951 The default location of the Postfix main.cf and master.cf configuration
952 files. This can be overruled via the following mechanisms:
953 • The MAIL_CONFIG environment variable (daemon processes and com‐
955 mands).
956 • The "-c" command-line option (commands only).
958 With Postfix commands that run with set-gid privileges, a config_direc‐
960 tory override either requires root privileges, or it requires that the
961 directory is listed with the alternate_config_directories parameter in
962 the default main.cf file.
963
965 After sending a "your message is delayed" notification, inform the
966 sender when the delay clears up. This can result in a sudden burst of
967 notifications at the end of a prolonged network outage, and is there‐
968 fore disabled by default.
969 See also: delay_warning_time.
971 This feature is available in Postfix 3.0 and later.
973
975 Time limit for connection cache connect, send or receive operations.
976 The time limit is enforced in the client.
977 This feature is available in Postfix 2.3 and later.
979
981 The name of the scache(8) connection cache service. This service main‐
982 tains a limited pool of cached sessions.
983 This feature is available in Postfix 2.2 and later.
985
987 How frequently the scache(8) server logs usage statistics with connec‐
988 tion cache hit and miss rates for logical destinations and for physical
989 endpoints.
990
992 The maximal time-to-live value that the scache(8) connection cache
993 server allows. Requests that specify a larger TTL will be stored with
994 the maximum allowed TTL. The purpose of this additional control is to
995 protect the infrastructure against careless people. The cache TTL is
996 already bounded by $max_idle.
997
999 After the message is queued, send the entire message to the specified
1000 transport:destination. The transport name specifies the first field of
1001 a mail delivery agent definition in master.cf; the syntax of the
1002 next-hop destination is described in the manual page of the correspond‐
1003 ing delivery agent. More information about external content filters is
1004 in the Postfix FILTER_README file.
1005 Notes:
1007 • This setting has lower precedence than a FILTER action that is
1009 specified in an access(5), header_checks(5) or body_checks(5)
1010 table.
1011 • The meaning of an empty next-hop filter destination is version
1013 dependent. Postfix 2.7 and later will use the recipient domain;
1014 earlier versions will use $myhostname. Specify "default_fil‐
1015 ter_nexthop = $myhostname" for compatibility with Postfix 2.6 or
1016 earlier, or specify a content_filter value with an explicit
1017 next-hop destination.
1018
1020 Search path for Cyrus SASL application configuration files, currently
1021 used only to locate the $smtpd_sasl_path.conf file. Specify zero or
1022 more directories separated by a colon character, or an empty value to
1023 use Cyrus SASL's built-in search path.
1024 This feature is available in Postfix 2.5 and later when compiled with
1026 Cyrus SASL 2.1.22 or later.
1027
1029 The directory with Postfix support programs and daemon programs. These
1030 should not be invoked directly by humans. The directory must be owned
1031 by root.
1032
1034 How a Postfix daemon process handles errors while opening lookup ta‐
1035 bles: gradual degradation or immediate termination.
1036 no (default)
1038 Gradual degradation: a daemon process logs a message of type
1039 "error" and continues execution with reduced functionality. Fea‐
1040 tures that do not depend on the unavailable table will work nor‐
1041 mally, while features that depend on the table will result in a
1042 type "warning" message.
1043 When the notify_classes parameter value contains the "data"
1044 class, the Postfix SMTP server and client will report tran‐
1045 scripts of sessions with an error because a table is unavail‐
1046 able.
1047 yes (historical behavior)
1049 Immediate termination: a daemon process logs a type "fatal" mes‐
1050 sage and terminates immediately. This option reduces the number
1051 of possible code paths through Postfix, and may therefore be
1052 slightly more secure than the default.
1053 For the sake of sanity, the number of type "error" messages is limited
1055 to 13 over the lifetime of a daemon process.
1056 This feature is available in Postfix 2.9 and later.
1058
1060 How much time a Postfix daemon process may take to handle a request be‐
1061 fore it is terminated by a built-in watchdog timer.
1062 Time units: s (seconds), m (minutes), h (hours), d (days), w (weeks).
1064 The default time unit is s (seconds).
1065
1067 The directory with Postfix-writable data files (for example: caches,
1068 pseudo-random numbers). This directory must be owned by the mail_owner
1069 account, and must not be shared with non-Postfix software.
1070 This feature is available in Postfix 2.5 and later.
1072
1074 The increment in verbose logging level when a nexthop destination, re‐
1075 mote client or server name or network address matches a pattern given
1076 with the debug_peer_list parameter.
1077 Per-nexthop debug logging is available in Postfix 3.6 and later.
1079
1081 Optional list of nexthop destination, remote client or server name or
1082 network address patterns that, if matched, cause the verbose logging
1083 level to increase by the amount specified in $debug_peer_level.
1084 Per-nexthop debug logging is available in Postfix 3.6 and later.
1086 Specify domain names, network/netmask patterns, "/file/name" patterns
1088 or "type:table" lookup tables. The right-hand side result from
1089 "type:table" lookups is ignored.
1090 Pattern matching of domain names is controlled by the presence or ab‐
1092 sence of "debug_peer_list" in the parent_domain_matches_subdomains pa‐
1093 rameter value.
1094 Examples:
1096 debug_peer_list = 127.0.0.1
1098 debug_peer_list = example.com
1099
1101 The external command to execute when a Postfix daemon program is in‐
1102 voked with the -D option.
1103 Use "command .. & sleep 5" so that the debugger can attach before the
1105 process marches on. If you use an X-based debugger, be sure to set up
1106 your XAUTHORITY environment variable before starting Postfix.
1107 Note: the command is subject to $name expansion, before it is passed to
1109 the default command interpreter. Specify "$$" to produce a single "$"
1110 character.
1111 Example:
1113 debugger_command =
1115 PATH=/usr/bin:/usr/X11R6/bin
1116 ddd $daemon_directory/$process_name $process_id & sleep 5
1117
1119 The default database type for use in newaliases(1), postalias(1) and
1120 postmap(1) commands. On many UNIX systems the default type is either
1121 dbm or hash. The default setting is frozen when the Postfix system is
1122 built.
1123 Examples:
1125 default_database_type = hash
1127 default_database_type = dbm
1128
1130 How often the Postfix queue manager's scheduler is allowed to preempt
1131 delivery of one message with another.
1132 Each transport maintains a so-called "available delivery slot counter"
1134 for each message. One message can be preempted by another one when the
1135 other message can be delivered using no more delivery slots (i.e., in‐
1136 vocations of delivery agents) than the current message counter has ac‐
1137 cumulated (or will eventually accumulate - see about slot loans below).
1138 This parameter controls how often is the counter incremented - it hap‐
1139 pens after each default_delivery_slot_cost recipients have been deliv‐
1140 ered.
1141 The cost of 0 is used to disable the preempting scheduling completely.
1143 The minimum value the scheduling algorithm can use is 2 - use it if you
1144 want to maximize the message throughput rate. Although there is no max‐
1145 imum, it doesn't make much sense to use values above say 50.
1146 The only reason why the value of 2 is not the default is the way this
1148 parameter affects the delivery of mailing-list mail. In the worst case,
1149 delivery can take somewhere between (cost+1/cost) and (cost/cost-1)
1150 times more than if the preemptive scheduler was disabled. The default
1151 value of 5 turns out to provide reasonable message response times while
1152 making sure the mailing-list deliveries are not extended by more than
1153 20-25 percent even in the worst case.
1154 Use transport_delivery_slot_cost to specify a transport-specific over‐
1156 ride, where transport is the master.cf name of the message delivery
1157 transport.
1158 Examples:
1160 default_delivery_slot_cost = 0
1162 default_delivery_slot_cost = 2
1163
1165 The default value for transport-specific _delivery_slot_discount set‐
1166 tings.
1167 This parameter speeds up the moment when a message preemption can hap‐
1169 pen. Instead of waiting until the full amount of delivery slots re‐
1170 quired is available, the preemption can happen when transport_deliv‐
1171 ery_slot_discount percent of the required amount plus transport_deliv‐
1172 ery_slot_loan still remains to be accumulated. Note that the full
1173 amount will still have to be accumulated before another preemption can
1174 take place later.
1175 Use transport_delivery_slot_discount to specify a transport-specific
1177 override, where transport is the master.cf name of the message delivery
1178 transport.
1179
1181 The default value for transport-specific _delivery_slot_loan settings.
1182 This parameter speeds up the moment when a message preemption can hap‐
1184 pen. Instead of waiting until the full amount of delivery slots re‐
1185 quired is available, the preemption can happen when transport_deliv‐
1186 ery_slot_discount percent of the required amount plus transport_deliv‐
1187 ery_slot_loan still remains to be accumulated. Note that the full
1188 amount will still have to be accumulated before another preemption can
1189 take place later.
1190 Use transport_delivery_slot_loan to specify a transport-specific over‐
1192 ride, where transport is the master.cf name of the message delivery
1193 transport.
1194
1196 Optional filter to replace the delivery status code or explanatory text
1197 of successful or unsuccessful deliveries. This does not allow the re‐
1198 placement of a successful status code (2.X.X) with an unsuccessful sta‐
1199 tus code (4.X.X or 5.X.X) or vice versa.
1200 Note: the (smtp|lmtp)_delivery_status_filter is applied only once per
1202 recipient: when delivery is successful, when delivery is rejected with
1203 5XX, or when there are no more alternate MX or A destinations. Use
1204 smtp_reply_filter or lmtp_reply_filter to inspect responses for all de‐
1205 livery attempts.
1206 The following parameters can be used to implement a filter for specific
1208 delivery agents: lmtp_delivery_status_filter, local_delivery_sta‐
1209 tus_filter, pipe_delivery_status_filter, smtp_delivery_status_filter or
1210 virtual_delivery_status_filter. These parameters support the same fil‐
1211 ter syntax as described here.
1212 Specify zero or more "type:table" lookup table names, separated by
1214 comma or whitespace. For each successful or unsuccessful delivery to a
1215 recipient, the tables are queried in the specified order with one line
1216 of text that is structured as follows:
1217 enhanced-status-code SPACE explanatory-text
1219 The first table match wins. The lookup result must have the same struc‐
1221 ture as the query, a successful status code (2.X.X) must be replaced
1222 with a successful status code, an unsuccessful status code (4.X.X or
1223 5.X.X) must be replaced with an unsuccessful status code, and the ex‐
1224 planatory text field must be non-empty. Other results will result in a
1225 warning.
1226 Example 1: convert specific soft TLS errors into hard errors, by over‐
1228 riding the first number in the enhanced status code.
1229 /etc/postfix/main.cf:
1231 smtp_delivery_status_filter = pcre:/etc/postfix/smtp_dsn_filter
1232 /etc/postfix/smtp_dsn_filter:
1234 /^4(\.\d+\.\d+ TLS is required, but host \S+ refused to start TLS: .+)/
1235 5$1
1236 /^4(\.\d+\.\d+ TLS is required, but was not offered by host .+)/
1237 5$1
1238 # Do not change the following into hard bounces. They may
1239 # result from a local configuration problem.
1240 # 4.\d+.\d+ TLS is required, but our TLS engine is unavailable
1241 # 4.\d+.\d+ TLS is required, but unavailable
1242 # 4.\d+.\d+ Cannot start TLS: handshake failure
1243 Example 2: censor the per-recipient delivery status text so that it
1245 does not reveal the destination command or filename when a remote
1246 sender requests confirmation of successful delivery.
1247 /etc/postfix/main.cf:
1249 local_delivery_status_filter = pcre:/etc/postfix/local_dsn_filter
1250 /etc/postfix/local_dsn_filter:
1252 /^(2\S+ delivered to file).+/ $1
1253 /^(2\S+ delivered to command).+/ $1
1254 Notes:
1256 • This feature will NOT override the soft_bounce safety net.
1258 • This feature will change the enhanced status code and text that
1260 is logged to the maillog file, and that is reported to the
1261 sender in delivery confirmation or non-delivery notifications.
1262 This feature is available in Postfix 3.0 and later.
1264
1266 How many pseudo-cohorts must suffer connection or handshake failure be‐
1267 fore a specific destination is considered unavailable (and further de‐
1268 livery is suspended). Specify zero to disable this feature. A destina‐
1269 tion's pseudo-cohort failure count is reset each time a delivery com‐
1270 pletes without connection or handshake failure for that specific desti‐
1271 nation.
1272 A pseudo-cohort is the number of deliveries equal to a destination's
1274 delivery concurrency.
1275 Use transport_destination_concurrency_failed_cohort_limit to specify a
1277 transport-specific override, where transport is the master.cf name of
1278 the message delivery transport.
1279 This feature is available in Postfix 2.5. The default setting is com‐
1281 patible with earlier Postfix versions.
1282
1284 The default maximal number of parallel deliveries to the same destina‐
1285 tion. This is the default limit for delivery via the lmtp(8), pipe(8),
1286 smtp(8) and virtual(8) delivery agents. With per-destination recipient
1287 limit > 1, a destination is a domain, otherwise it is a recipient.
1288 Use transport_destination_concurrency_limit to specify a transport-spe‐
1290 cific override, where transport is the master.cf name of the message
1291 delivery transport.
1292
1294 The per-destination amount of delivery concurrency negative feedback,
1295 after a delivery completes with a connection or handshake failure.
1296 Feedback values are in the range 0..1 inclusive. With negative feed‐
1297 back, concurrency is decremented at the beginning of a sequence of
1298 length 1/feedback. This is unlike positive feedback, where concurrency
1299 is incremented at the end of a sequence of length 1/feedback.
1300 As of Postfix version 2.5, negative feedback cannot reduce delivery
1302 concurrency to zero. Instead, a destination is marked dead (further
1303 delivery suspended) after the failed pseudo-cohort count reaches $de‐
1304 fault_destination_concurrency_failed_cohort_limit (or $transport_desti‐
1305 nation_concurrency_failed_cohort_limit). To make the scheduler com‐
1306 pletely immune to connection or handshake failures, specify a zero
1307 feedback value and a zero failed pseudo-cohort limit.
1308 Specify one of the following forms:
1310 number
1312 number / number
1314 Constant feedback. The value must be in the range 0..1 inclu‐
1315 sive. The default setting of "1" is compatible with Postfix
1316 versions before 2.5, where a destination's delivery concurrency
1317 is throttled down to zero (and further delivery suspended) after
1318 a single failed pseudo-cohort.
1319 number / concurrency
1321 Variable feedback of "number / (delivery concurrency)". The
1322 number must be in the range 0..1 inclusive. With number equal to
1323 "1", a destination's delivery concurrency is decremented by 1
1324 after each failed pseudo-cohort.
1325 A pseudo-cohort is the number of deliveries equal to a destination's
1327 delivery concurrency.
1328 Use transport_destination_concurrency_negative_feedback to specify a
1330 transport-specific override, where transport is the master.cf name of
1331 the message delivery transport.
1332 This feature is available in Postfix 2.5. The default setting is com‐
1334 patible with earlier Postfix versions.
1335
1337 The per-destination amount of delivery concurrency positive feedback,
1338 after a delivery completes without connection or handshake failure.
1339 Feedback values are in the range 0..1 inclusive. The concurrency in‐
1340 creases until it reaches the per-destination maximal concurrency limit.
1341 With positive feedback, concurrency is incremented at the end of a se‐
1342 quence with length 1/feedback. This is unlike negative feedback, where
1343 concurrency is decremented at the start of a sequence of length 1/feed‐
1344 back.
1345 Specify one of the following forms:
1347 number
1349 number / number
1351 Constant feedback. The value must be in the range 0..1 inclu‐
1352 sive. The default setting of "1" is compatible with Postfix ver‐
1353 sions before 2.5, where a destination's delivery concurrency
1354 doubles after each successful pseudo-cohort.
1355 number / concurrency
1357 Variable feedback of "number / (delivery concurrency)". The
1358 number must be in the range 0..1 inclusive. With number equal to
1359 "1", a destination's delivery concurrency is incremented by 1
1360 after each successful pseudo-cohort.
1361 A pseudo-cohort is the number of deliveries equal to a destination's
1363 delivery concurrency.
1364 Use transport_destination_concurrency_positive_feedback to specify a
1366 transport-specific override, where transport is the master.cf name of
1367 the message delivery transport.
1368 This feature is available in Postfix 2.5 and later.
1370
1372 The default amount of delay that is inserted between individual message
1373 deliveries to the same destination and over the same message delivery
1374 transport. Specify a non-zero value to rate-limit those message deliv‐
1375 eries to at most one per $default_destination_rate_delay.
1376 The resulting behavior depends on the value of the corresponding
1378 per-destination recipient limit.
1379 • With a corresponding per-destination recipient limit > 1, the
1381 rate delay specifies the time between deliveries to the same do‐
1382 main. Different domains are delivered in parallel, subject to
1383 the process limits specified in master.cf.
1384 • With a corresponding per-destination recipient limit equal to 1,
1386 the rate delay specifies the time between deliveries to the same
1387 recipient. Different recipients are delivered in parallel, sub‐
1388 ject to the process limits specified in master.cf.
1389 To enable the delay, specify a non-zero time value (an integral value
1391 plus an optional one-letter suffix that specifies the time unit).
1392 Time units: s (seconds), m (minutes), h (hours), d (days), w (weeks).
1394 The default time unit is s (seconds).
1395 NOTE: the delay is enforced by the queue manager. The delay timer state
1397 does not survive "postfix reload" or "postfix stop".
1398 Use transport_destination_rate_delay to specify a transport-specific
1400 override, where transport is the master.cf name of the message delivery
1401 transport.
1402 NOTE: with a non-zero _destination_rate_delay, specify a transport_des‐
1404 tination_concurrency_failed_cohort_limit of 10 or more to prevent Post‐
1405 fix from deferring all mail for the same destination after only one
1406 connection or handshake error.
1407 This feature is available in Postfix 2.5 and later.
1409
1411 The default maximal number of recipients per message delivery. This is
1412 the default limit for delivery via the lmtp(8), pipe(8), smtp(8) and
1413 virtual(8) delivery agents.
1414 Setting this parameter to a value of 1 affects email deliveries as fol‐
1416 lows:
1417 • It changes the meaning of the corresponding per-destination con‐
1419 currency limit, from concurrency of deliveries to the same do‐
1420 main into concurrency of deliveries to the same recipient. Dif‐
1421 ferent recipients are delivered in parallel, subject to the
1422 process limits specified in master.cf.
1423 • It changes the meaning of the corresponding per-destination rate
1425 delay, from the delay between deliveries to the same domain into
1426 the delay between deliveries to the same recipient. Again, dif‐
1427 ferent recipients are delivered in parallel, subject to the
1428 process limits specified in master.cf.
1429 • It changes the meaning of other corresponding per-destination
1431 settings in a similar manner, from settings for delivery to the
1432 same domain into settings for delivery to the same recipient.
1433 Use transport_destination_recipient_limit to specify a transport-spe‐
1435 cific override, where transport is the master.cf name of the message
1436 delivery transport.
1437
1439 The default value for the extra per-transport limit imposed on the num‐
1440 ber of in-memory recipients. This extra recipient space is reserved
1441 for the cases when the Postfix queue manager's scheduler preempts one
1442 message with another and suddenly needs some extra recipients slots for
1443 the chosen message in order to avoid performance degradation.
1444 Use transport_extra_recipient_limit to specify a transport-specific
1446 override, where transport is the master.cf name of the message delivery
1447 transport.
1448
1450 When a content_filter or FILTER request specifies no explicit next-hop
1451 destination, use $default_filter_nexthop instead; when that value is
1452 empty, use the domain in the recipient address. Specify "default_fil‐
1453 ter_nexthop = $myhostname" for compatibility with Postfix version 2.6
1454 and earlier, or specify an explicit next-hop destination with each con‐
1455 tent_filter value or FILTER action.
1456 This feature is available in Postfix 2.7 and later.
1458
1460 How many recipients a message must have in order to invoke the Postfix
1461 queue manager's scheduling algorithm at all. Messages which would
1462 never accumulate at least this many delivery slots (subject to slot
1463 cost parameter as well) are never preempted.
1464 Use transport_minimum_delivery_slots to specify a transport-specific
1466 override, where transport is the master.cf name of the message delivery
1467 transport.
1468
1470 The default rights used by the local(8) delivery agent for delivery to
1471 external file or command. These rights are used when delivery is re‐
1472 quested from an aliases(5) file that is owned by root, or when delivery
1473 is done on behalf of root. DO NOT SPECIFY A PRIVILEGED USER OR THE
1474 POSTFIX OWNER.
1475
1477 The default maximal number of Postfix child processes that provide a
1478 given service. This limit can be overruled for specific services in the
1479 master.cf file.
1480
1482 The default Postfix SMTP server response template for a request that is
1483 rejected by an RBL-based restriction. This template can be overruled by
1484 specific entries in the optional rbl_reply_maps lookup table.
1485 This feature is available in Postfix 2.0 and later.
1487 The template does not support Postfix configuration parameter $name
1489 substitution. Instead, it supports exactly one level of $name substitu‐
1490 tion for the following attributes:
1491 $client
1493 The client hostname and IP address, formatted as name[address].
1494 $client_address
1496 The client IP address.
1497 $client_name
1499 The client hostname or "unknown". See reject_un‐
1500 known_client_hostname for more details.
1501 $reverse_client_name
1503 The client hostname from address->name lookup, or "unknown".
1504 See reject_unknown_reverse_client_hostname for more details.
1505 $helo_name
1507 The hostname given in HELO or EHLO command or empty string.
1508 $rbl_class
1510 The denylisted entity type: Client host, Helo command, Sender
1511 address, or Recipient address.
1512 $rbl_code
1514 The numerical SMTP response code, as specified with the
1515 maps_rbl_reject_code configuration parameter. Note: The numeri‐
1516 cal SMTP response code is required, and must appear at the start
1517 of the reply. With Postfix version 2.3 and later this informa‐
1518 tion may be followed by an RFC 3463 enhanced status code.
1519 $rbl_domain
1521 The RBL domain where $rbl_what is denylisted.
1522 $rbl_reason
1524 The reason why $rbl_what is denylisted, or an empty string.
1525 $rbl_what
1527 The entity that is denylisted (an IP address, a hostname, a do‐
1528 main name, or an email address whose domain was denylisted).
1529 $recipient
1531 The recipient address or <> in case of the null address.
1532 $recipient_domain
1534 The recipient domain or empty string.
1535 $recipient_name
1537 The recipient address localpart or <> in case of null address.
1538 $sender
1540 The sender address or <> in case of the null address.
1541 $sender_domain
1543 The sender domain or empty string.
1544 $sender_name
1546 The sender address localpart or <> in case of the null address.
1547 ${name?text}
1549 Expands to `text' if $name is not empty.
1550 ${name:text}
1552 Expands to `text' if $name is empty.
1553 Instead of $name you can also specify ${name} or $(name).
1555 Note: when an enhanced status code is specified in an RBL reply tem‐
1557 plate, it is subject to modification. The following transformations
1558 are needed when the same RBL reply template is used for client, helo,
1559 sender, or recipient access restrictions.
1560 • When rejecting a sender address, the Postfix SMTP server will
1562 transform a recipient DSN status (e.g., 4.1.1-4.1.6) into the
1563 corresponding sender DSN status, and vice versa.
1564 • When rejecting non-address information (such as the HELO command
1566 argument or the client hostname/address), the Postfix SMTP
1567 server will transform a sender or recipient DSN status into a
1568 generic non-address DSN status (e.g., 4.0.0).
1569
1571 The default per-transport upper limit on the number of in-memory recip‐
1572 ients. These limits take priority over the global qmgr_message_recipi‐
1573 ent_limit after the message has been assigned to the respective trans‐
1574 ports. See also default_extra_recipient_limit and qmgr_message_recipi‐
1575 ent_minimum.
1576 Use transport_recipient_limit to specify a transport-specific override,
1578 where transport is the master.cf name of the message delivery trans‐
1579 port.
1580
1582 The default per-transport maximum delay between recipients refills.
1583 When not all message recipients fit into the memory at once, keep load‐
1584 ing more of them at least once every this many seconds. This is used
1585 to make sure the recipients are refilled in timely manner even when
1586 $default_recipient_refill_limit is too high for too slow deliveries.
1587 Use transport_recipient_refill_delay to specify a transport-specific
1589 override, where transport is the master.cf name of the message delivery
1590 transport.
1591 This feature is available in Postfix 2.4 and later.
1593
1595 The default per-transport limit on the number of recipients refilled at
1596 once. When not all message recipients fit into the memory at once,
1597 keep loading more of them in batches of at least this many at a time.
1598 See also $default_recipient_refill_delay, which may result in recipient
1599 batches lower than this when this limit is too high for too slow deliv‐
1600 eries.
1601 Use transport_recipient_refill_limit to specify a transport-specific
1603 override, where transport is the master.cf name of the message delivery
1604 transport.
1605 This feature is available in Postfix 2.4 and later.
1607
1609 The default mail delivery transport and next-hop destination for desti‐
1610 nations that do not match $mydestination, $inet_interfaces, $proxy_in‐
1611 terfaces, $virtual_alias_domains, $virtual_mailbox_domains, or $re‐
1612 lay_domains. This information can be overruled with the sender_depen‐
1613 dent_default_transport_maps parameter and with the transport(5) table.
1614 In order of decreasing precedence, the nexthop destination is taken
1616 from $sender_dependent_default_transport_maps, $default_transport,
1617 $sender_dependent_relayhost_maps, $relayhost, or from the recipient do‐
1618 main.
1619 Specify a string of the form transport:nexthop, where transport is the
1621 name of a mail delivery transport defined in master.cf. The :nexthop
1622 destination is optional; its syntax is documented in the manual page of
1623 the corresponding delivery agent. In the case of SMTP or LMTP, specify
1624 one or more destinations separated by comma or whitespace (with Postfix
1625 3.5 and later).
1626 Example:
1628 default_transport = uucp:relayhostname
1630
1632 The default amount of delay that is inserted between individual message
1633 deliveries over the same message delivery transport, regardless of des‐
1634 tination. Specify a non-zero value to rate-limit those message deliver‐
1635 ies to at most one per $default_transport_rate_delay.
1636 Use transport_transport_rate_delay to specify a transport-specific
1638 override, where the initial transport is the master.cf name of the mes‐
1639 sage delivery transport.
1640 Example: throttle outbound SMTP mail to at most 3 deliveries per
1642 minute.
1643 /etc/postfix/main.cf:
1645 smtp_transport_rate_delay = 20s
1646 To enable the delay, specify a non-zero time value (an integral value
1648 plus an optional one-letter suffix that specifies the time unit).
1649 Time units: s (seconds), m (minutes), h (hours), d (days), w (weeks).
1651 The default time unit is s (seconds).
1652 NOTE: the delay is enforced by the queue manager.
1654 This feature is available in Postfix 3.1 and later.
1656
1658 The two default VERP delimiter characters. These are used when no ex‐
1659 plicit delimiters are specified with the SMTP XVERP command or with the
1660 "sendmail -V" command-line option. Specify characters that are allowed
1661 by the verp_delimiter_filter setting.
1662 This feature is available in Postfix 1.1 and later.
1664
1666 The numerical Postfix SMTP server response code when a remote SMTP
1667 client request is rejected by the "defer" restriction.
1668 Do not change this unless you have a complete understanding of RFC
1670 5321.
1671
1673 The name of the defer service. This service is implemented by the
1674 bounce(8) daemon and maintains a record of failed delivery attempts and
1675 generates non-delivery notifications.
1676 This feature is available in Postfix 2.0 and later.
1678
1680 The names of message delivery transports that should not deliver mail
1681 unless someone issues "sendmail -q" or equivalent. Specify zero or more
1682 names of mail delivery transports names that appear in the first field
1683 of master.cf.
1684 Example:
1686 defer_transports = smtp
1688
1690 The maximal number of digits after the decimal point when logging
1691 sub-second delay values. Specify a number in the range 0..6.
1692 Large delay values are rounded off to an integral number seconds; delay
1694 values below the delay_logging_resolution_limit are logged as "0", and
1695 delay values under 100s are logged with at most two-digit precision.
1696 The format of the "delays=a/b/c/d" logging is as follows:
1698 • a = time from message arrival to last active queue entry
1700 • b = time from last active queue entry to connection setup
1702 • c = time in connection setup, including DNS, EHLO and STARTTLS
1704 • d = time in message transmission
1706 This feature is available in Postfix 2.3 and later.
1708
1710 The recipient of postmaster notifications with the message headers of
1711 mail that cannot be delivered within $delay_warning_time time units.
1712 See also: delay_warning_time, notify_classes.
1714
1716 The time after which the sender receives a copy of the message headers
1717 of mail that is still queued. The confirm_delay_cleared parameter con‐
1718 trols sender notification when the delay clears up.
1719 To enable this feature, specify a non-zero time value (an integral
1721 value plus an optional one-letter suffix that specifies the time unit).
1722 Time units: s (seconds), m (minutes), h (hours), d (days), w (weeks).
1724 The default time unit is h (hours).
1725 See also: delay_notice_recipient, notify_classes, confirm_de‐
1727 lay_cleared.
1728
1730 The maximal number of attempts to acquire an exclusive lock on a mail‐
1731 box file or bounce(8) logfile.
1732
1734 The time between attempts to acquire an exclusive lock on a mailbox
1735 file or bounce(8) logfile.
1736 Time units: s (seconds), m (minutes), h (hours), d (days), w (weeks).
1738 The default time unit is s (seconds).
1739
1741 Make the queue manager's feedback algorithm verbose for performance
1742 analysis purposes.
1743 This feature is available in Postfix 2.5 and later.
1745
1747 Automatically detect 8BITMIME body content by looking at Content-Trans‐
1748 fer-Encoding: message headers; historically, this behavior was
1749 hard-coded to be "always on".
1750 This feature is available in Postfix 2.5 and later.
1752
1754 Disable DNS lookups in the Postfix SMTP and LMTP clients. When dis‐
1755 abled, hosts are looked up with the getaddrinfo() system library rou‐
1756 tine which normally also looks in /etc/hosts. As of Postfix 2.11, this
1757 parameter is deprecated; use smtp_dns_support_level instead.
1758 DNS lookups are enabled by default.
1760
1762 Turn off MIME processing while receiving mail. This means that no spe‐
1763 cial treatment is given to Content-Type: message headers, and that all
1764 text after the initial message headers is considered to be part of the
1765 message body.
1766 This feature is available in Postfix 2.0 and later.
1768 Mime input processing is enabled by default, and is needed in order to
1770 recognize MIME headers in message content.
1771
1773 Disable the conversion of 8BITMIME format to 7BIT format. Mime output
1774 conversion is needed when the destination does not advertise 8BITMIME
1775 support.
1776 This feature is available in Postfix 2.0 and later.
1778
1780 Disable sending one bounce report per recipient.
1781 The default, one per recipient, is what ezmlm needs.
1783 This feature is available in Postfix 1.1 and later.
1785
1787 Disable the SMTP VRFY command. This stops some techniques used to har‐
1788 vest email addresses.
1789 Example:
1791 disable_vrfy_command = no
1793
1795 Enable a workaround for future libc incompatibility. The Postfix imple‐
1796 mentation of RFC 2308 negative reply caching relies on the promise that
1797 res_query() and res_search() invoke res_send(), which returns the
1798 server response in an application buffer even if the requested record
1799 does not exist. If this promise is broken, specify "yes" to enable a
1800 workaround for DNS reputation lookups.
1801 This feature is available in Postfix 3.1 and later.
1803
1805 A debugging aid to artificially delay DNS responses.
1806 This feature is available in Postfix 2.8.
1808
1810 The name of the dnsblog(8) service entry in master.cf. This service
1811 performs DNS allow/denylist lookups.
1812 This feature is available in Postfix 2.8 and later.
1814
1816 The DNS query type (default: "ns") and DNS query name (default: ".")
1817 that Postfix may use to determine whether DNSSEC validation is avail‐
1818 able.
1819 Background: DNSSEC validation is needed for Postfix DANE support; this
1821 ensures that Postfix receives TLSA records with secure TLS server cer‐
1822 tificate info. When DNSSEC validation is unavailable, mail deliveries
1823 using opportunistic DANE will not be protected by server certificate
1824 info in TLSA records, and mail deliveries using mandatory DANE will not
1825 be made at all.
1826 By default, a Postfix process will send a DNSSEC probe after 1) the
1828 process made a DNS query that requested DNSSEC validation, 2) the
1829 process did not receive a DNSSEC validated response to this query or to
1830 an earlier query, and 3) the process did not already send a DNSSEC
1831 probe.
1832 When the DNSSEC probe has no response, or when the response is not
1834 DNSSEC validated, Postfix logs a warning that DNSSEC validation may be
1835 unavailable.
1836 Example:
1838 warning: DNSSEC validation may be unavailable
1840 warning: reason: dnssec_probe 'ns:.' received a response that is not DNSSEC validated
1841 warning: reason: dnssec_probe 'ns:.' received no response: Server failure
1842 Possible reasons why DNSSEC validation may be unavailable:
1844 • The local /etc/resolv.conf file specifies a DNS resolver that
1846 does not validate DNSSEC signatures (that's $queue_direc‐
1847 tory/etc/resolv.conf when a Postfix daemon runs in a chroot
1848 jail).
1849 • The local system library does not pass on the "DNSSEC validated"
1851 bit to Postfix, or Postfix does not know how to ask the library
1852 to do that.
1853 By default, the DNSSEC probe asks for the DNS root zone NS records, be‐
1855 cause resolvers should always have that information cached. If Postfix
1856 runs on a network where the DNS root zone is not reachable, specify a
1857 different probe, or specify an empty dnssec_probe value to disable the
1858 feature.
1859 This feature is available in Postfix 3.6 and later. It was backported
1861 to Postfix versions 3.5.9, 3.4.19, 3.3.16. 3.2.21.
1862
1864 Don't remove queue files and save them to the "saved" mail queue. This
1865 is a debugging aid. To inspect the envelope information and content of
1866 a Postfix queue file, use the postcat(1) command.
1867
1869 The sender address of postmaster notifications that are generated by
1870 the mail system. All mail to this address is silently discarded, in or‐
1871 der to terminate mail bounce loops.
1872
1874 The maximal number of addresses remembered by the address duplicate
1875 filter for aliases(5) or virtual(5) alias expansion, or for showq(8)
1876 queue displays.
1877
1879 The sender_dependent_default_transport_maps search string that will be
1880 used instead of the null sender address.
1881 This feature is available in Postfix 2.7 and later.
1883
1885 The lookup key to be used in local_login_sender_maps tables, instead of
1886 the null sender address.
1887 This feature is available in Postfix 3.6 and later.
1889
1891 The recipient of mail addressed to the null address. Postfix does not
1892 accept such addresses in SMTP commands, but they may still be created
1893 locally as the result of configuration or software error.
1894
1896 The sender_dependent_relayhost_maps search string that will be used in‐
1897 stead of the null sender address.
1898 This feature is available in Postfix 2.5 and later. With earlier ver‐
1900 sions, sender_dependent_relayhost_maps lookups were skipped for the
1901 null sender address.
1902
1904 Report mail delivery errors to the address specified with the non-stan‐
1905 dard Errors-To: message header, instead of the envelope sender address
1906 (this feature is removed with Postfix version 2.2, is turned off by de‐
1907 fault with Postfix version 2.1, and is always turned on with older
1908 Postfix versions).
1909
1911 Enable 'transitional' compatibility between IDNA2003 and IDNA2008, when
1912 converting UTF-8 domain names to/from the ASCII form that is used for
1913 DNS lookups. Specify "yes" for compatibility with Postfix <= 3.1 (not
1914 recommended). This affects the conversion of domain names that contain
1915 for example the German sz and the Greek zeta. See http://uni‐
1916 code.org/cldr/utility/idna.jsp for more examples.
1917 This feature is available in Postfix 3.2 and later.
1919
1921 Enable long, non-repeating, queue IDs (queue file names). The benefit
1922 of non-repeating names is simpler logfile analysis and easier queue mi‐
1923 gration (there is no need to run "postsuper" to change queue file names
1924 that don't match their message file inode number).
1925 Note: see below for how to convert long queue file names to Postfix <=
1927 2.8.
1928 Changing the parameter value to "yes" has the following effects:
1930 • Existing queue file names are not affected.
1932 • New queue files are created with names such as 3Pt2mN2VXxznjll.
1934 These are encoded in a 52-character alphabet that contains dig‐
1935 its (0-9), upper-case letters (B-Z) and lower-case letters
1936 (b-z). For safety reasons the vowels (AEIOUaeiou) are excluded
1937 from the alphabet. The name format is: 6 or more characters for
1938 the time in seconds, 4 characters for the time in microseconds,
1939 the 'z'; the remainder is the file inode number encoded in the
1940 first 51 characters of the 52-character alphabet.
1941 • New messages have a Message-ID header with queueID@myhostname.
1943 • The mailq (postqueue -p) output has a wider Queue ID column.
1945 The number of whitespace-separated fields is not changed.
1946 • The hash_queue_depth algorithm uses the first characters of the
1948 queue file creation time in microseconds, after conversion into
1949 hexadecimal representation. This produces the same queue hashing
1950 behavior as if the queue file name was created with "en‐
1951 able_long_queue_ids = no".
1952 Changing the parameter value to "no" has the following effects:
1954 • Existing long queue file names are renamed to the short form
1956 (while running "postfix reload" or "postsuper").
1957 • New queue files are created with names such as C3CD21F3E90 from
1959 a hexadecimal alphabet that contains digits (0-9) and upper-case
1960 letters (A-F). The name format is: 5 characters for the time in
1961 microseconds; the remainder is the file inode number.
1962 • New messages have a Message-ID header with YYYYMMDDHH‐
1964 MMSS.queueid@myhostname, where YYYYMMDDHHMMSS are the year,
1965 month, day, hour, minute and second.
1966 • The mailq (postqueue -p) output has the same format as with
1968 Postfix <= 2.8.
1969 • The hash_queue_depth algorithm uses the first characters of the
1971 queue file name, with the hexadecimal representation of the file
1972 creation time in microseconds.
1973 Before migration to Postfix <= 2.8, the following commands are required
1975 to convert long queue file names into short names:
1976 # postfix stop
1978 # postconf enable_long_queue_ids=no
1979 # postsuper
1980 Repeat the postsuper command until it reports no more queue file name
1982 changes.
1983 This feature is available in Postfix 2.9 and later.
1985
1987 Enable support for the original recipient address after an address is
1988 rewritten to a different address (for example with aliasing or with
1989 canonical mapping).
1990 The original recipient address is used as follows:
1992 Final delivery
1994 With "enable_original_recipient = yes", the original recipient
1995 address is stored in the X-Original-To message header. This
1996 header may be used to distinguish between different recipients
1997 that share the same mailbox.
1998 Recipient deduplication
2000 With "enable_original_recipient = yes", the cleanup(8) daemon
2001 performs duplicate recipient elimination based on the content of
2002 (original recipient, maybe-rewritten recipient) pairs. Other‐
2003 wise, the cleanup(8) daemon performs duplicate recipient elimi‐
2004 nation based only on the maybe-rewritten recipient address.
2005 Note: with Postfix <= 3.2 the "setting enable_original_recipient = no"
2007 breaks address verification for addresses that are aliased or otherwise
2008 rewritten (Postfix is unable to store the address verification result
2009 under the original probe destination address; instead, it can store the
2010 result only under the rewritten address).
2011 This feature is available in Postfix 2.1 and later. Postfix version 2.0
2013 behaves as if this parameter is always set to yes. Postfix versions
2014 before 2.0 have no support for the original recipient address.
2015
2017 Enable non-delivery, success, and delay notifications that link to the
2018 original message by including a References: and In-Reply-To: header
2019 with the original Message-ID value. There are advantages and disadvan‐
2020 tages to consider.
2021 advantage
2023 This allows mail readers to present a delivery status notifica‐
2024 tion in the same email thread as the original message.
2025 disadvantage
2027 This makes it easy for users to mistakenly delete the whole
2028 email thread (all related messages), instead of deleting only
2029 the non-delivery notification.
2030 This feature is available in Postfix 3.6 and later.
2032
2034 The recipient of postmaster notifications about mail delivery problems
2035 that are caused by policy, resource, software or protocol errors.
2036 These notifications are enabled with the notify_classes parameter.
2037
2039 The name of the error(8) pseudo delivery agent. This service always re‐
2040 turns mail as undeliverable.
2041 This feature is available in Postfix 2.0 and later.
2043
2045 Restrict the characters that the local(8) delivery agent allows in
2046 $name expansions of $command_execution_directory. Characters outside
2047 the allowed set are replaced by underscores.
2048 This feature is available in Postfix 2.2 and later.
2050
2052 When delivering to an alias "aliasname" that has an "owner-aliasname"
2053 companion alias, set the envelope sender address to the expansion of
2054 the "owner-aliasname" alias. Normally, Postfix sets the envelope
2055 sender address to the name of the "owner-aliasname" alias.
2056
2058 The list of environment variables that a Postfix process will export to
2059 non-Postfix processes. The TZ variable is needed for sane time keeping
2060 on System-V-ish systems.
2061 Specify a list of names and/or name=value pairs, separated by white‐
2063 space or comma. Specify "{ name=value }" to protect whitespace or comma
2064 in parameter values (whitespace after the opening "{" and before the
2065 closing "}" is ignored). The form name=value is supported with Postfix
2066 version 2.1 and later; the use of {} is supported with Postfix 3.0 and
2067 later.
2068 Example:
2070 export_environment = TZ PATH=/bin:/usr/bin
2072
2074 The maximal number of recipient addresses that Postfix will extract
2075 from message headers when mail is submitted with "sendmail -t".
2076 This feature was removed in Postfix version 2.1.
2078
2080 Optional list of relay hosts for SMTP destinations that can't be found
2081 or that are unreachable. With Postfix 2.3 this parameter is renamed to
2082 smtp_fallback_relay.
2083 By default, mail is returned to the sender when a destination is not
2085 found, and delivery is deferred when a destination is unreachable.
2086 The fallback relays must be SMTP destinations. Specify a domain, host,
2088 host:port, [host]:port, [address] or [address]:port; the form [host]
2089 turns off MX lookups. If you specify multiple SMTP destinations, Post‐
2090 fix will try them in the specified order.
2091 Note: before Postfix 2.2, do not use the fallback_relay feature when
2093 relaying mail for a backup or primary MX domain. Mail would loop be‐
2094 tween the Postfix MX host and the fallback_relay host when the final
2095 destination is unavailable.
2096 • In main.cf specify "relay_transport = relay",
2098 • In master.cf specify "-o fallback_relay =" (i.e., empty) at the
2100 end of the relay entry.
2101 • In transport maps, specify "relay:nexthop..." as the right-hand
2103 side for backup or primary MX domain entries.
2104 Postfix version 2.2 and later will not use the fallback_relay feature
2106 for destinations that it is MX host for.
2107
2109 Optional message delivery transport that the local(8) delivery agent
2110 should use for names that are not found in the aliases(5) or UNIX pass‐
2111 word database.
2112 The precedence of local(8) delivery features from high to low is:
2114 aliases, .forward files, mailbox_transport_maps, mailbox_transport,
2115 mailbox_command_maps, mailbox_command, home_mailbox, mail_spool_direc‐
2116 tory, fallback_transport_maps, fallback_transport and luser_relay.
2117
2119 Optional lookup tables with per-recipient message delivery transports
2120 for recipients that the local(8) delivery agent could not find in the
2121 aliases(5) or UNIX password database.
2122 The precedence of local(8) delivery features from high to low is:
2124 aliases, .forward files, mailbox_transport_maps, mailbox_transport,
2125 mailbox_command_maps, mailbox_command, home_mailbox, mail_spool_direc‐
2126 tory, fallback_transport_maps, fallback_transport and luser_relay.
2127 For safety reasons, this feature does not allow $number substitutions
2129 in regular expression maps.
2130 This feature is available in Postfix 2.3 and later.
2132
2134 Optional list of destinations that are eligible for per-destination
2135 logfiles with mail that is queued to those destinations.
2136 By default, Postfix maintains "fast flush" logfiles only for destina‐
2138 tions that the Postfix SMTP server is willing to relay to (i.e. the de‐
2139 fault is: "fast_flush_domains = $relay_domains"; see the relay_domains
2140 parameter in the postconf(5) manual).
2141 Specify a list of hosts or domains, "/file/name" patterns or "type:ta‐
2143 ble" lookup tables, separated by commas and/or whitespace. Continue
2144 long lines by starting the next line with whitespace. A "/file/name"
2145 pattern is replaced by its contents; a "type:table" lookup table is
2146 matched when the domain or its parent domain appears as lookup key.
2147 Pattern matching of domain names is controlled by the presence or ab‐
2149 sence of "fast_flush_domains" in the parent_domain_matches_subdomains
2150 parameter value.
2151 Specify "fast_flush_domains =" (i.e., empty) to disable the feature al‐
2153 together.
2154
2156 The time after which an empty per-destination "fast flush" logfile is
2157 deleted.
2158 You can specify the time as a number, or as a number followed by a let‐
2160 ter that indicates the time unit: s=seconds, m=minutes, h=hours,
2161 d=days, w=weeks. The default time unit is days.
2162
2164 The time after which a non-empty but unread per-destination "fast
2165 flush" logfile needs to be refreshed. The contents of a logfile are
2166 refreshed by requesting delivery of all messages listed in the logfile.
2167 You can specify the time as a number, or as a number followed by a let‐
2169 ter that indicates the time unit: s=seconds, m=minutes, h=hours,
2170 d=days, w=weeks. The default time unit is hours.
2171
2173 Force specific internal tests to fail, to test the handling of errors
2174 that are difficult to reproduce otherwise.
2175
2177 The name of the flush(8) service. This service maintains per-destina‐
2178 tion logfiles with the queue file names of mail that is queued for
2179 those destinations.
2180 This feature is available in Postfix 2.0 and later.
2182
2184 The maximal number of attempts to fork() a child process.
2185
2187 The delay between attempts to fork() a child process.
2188 Time units: s (seconds), m (minutes), h (hours), d (days), w (weeks).
2190 The default time unit is s (seconds).
2191
2193 Restrict the characters that the local(8) delivery agent allows in
2194 $name expansions of $forward_path. Characters outside the allowed set
2195 are replaced by underscores.
2196
2198 The local(8) delivery agent search list for finding a .forward file
2199 with user-specified delivery methods. The first file that is found is
2200 used.
2201 The forward_path value is not subject to Postfix configuration parame‐
2203 ter $name expansion. Instead, the following $name expansions are done
2204 on forward_path before the search actually happens. The result of
2205 $name expansion is filtered with the character set that is specified
2206 with the forward_expansion_filter parameter.
2207 $user The recipient's username.
2209 $shell The recipient's login shell pathname.
2211 $home The recipient's home directory.
2213 $recipient
2215 The full recipient address.
2216 $extension
2218 The optional recipient address extension.
2219 $domain
2221 The recipient domain.
2222 $local The entire recipient localpart.
2224 $recipient_delimiter
2226 The address extension delimiter that was found in the recipient
2227 address (Postfix 2.11 and later), or the system-wide recipient
2228 address extension delimiter (Postfix 2.10 and earlier).
2229 ${name?value}
2231 Expands to value when $name is non-empty.
2232 ${name:value}
2234 Expands to value when $name is empty.
2235 Instead of $name you can also specify ${name} or $(name).
2237 Examples:
2239 forward_path = /var/forward/$user
2241 forward_path =
2242 /var/forward/$user/.forward$recipient_delimiter$extension,
2243 /var/forward/$user/.forward
2244
2246 Update the local(8) delivery agent's idea of the Delivered-To: address
2247 (see prepend_delivered_header) only once, at the start of a delivery
2248 attempt; do not update the Delivered-To: address while expanding
2249 aliases or .forward files.
2250 This feature is available in Postfix 2.3 and later. With older Postfix
2252 releases, the behavior is as if this parameter is set to "no". The old
2253 setting can be expensive with deeply nested aliases or .forward files.
2254 When an alias or .forward file changes the Delivered-To: address, it
2255 ties up one queue file and one cleanup process instance while mail is
2256 being forwarded.
2257
2259 The number of subdirectory levels for queue directories listed with the
2260 hash_queue_names parameter. Queue hashing is implemented by creating
2261 one or more levels of directories with one-character names. Origi‐
2262 nally, these directory names were equal to the first characters of the
2263 queue file name, with the hexadecimal representation of the file cre‐
2264 ation time in microseconds.
2265 With long queue file names, queue hashing produces the same results as
2267 with short names. The file creation time in microseconds is converted
2268 into hexadecimal form before the result is used for queue hashing. The
2269 base 16 encoding gives finer control over the number of subdirectories
2270 than is possible with the base 52 encoding of long queue file names.
2271 After changing the hash_queue_names or hash_queue_depth parameter, exe‐
2273 cute the command "postfix reload".
2274
2276 The names of queue directories that are split across multiple subdirec‐
2277 tory levels.
2278 Before Postfix version 2.2, the default list of hashed queues was sig‐
2280 nificantly larger. Claims about improvements in file system technology
2281 suggest that hashing of the incoming and active queues is no longer
2282 needed. Fewer hashed directories speed up the time needed to restart
2283 Postfix.
2284 After changing the hash_queue_names or hash_queue_depth parameter, exe‐
2286 cute the command "postfix reload".
2287
2289 The maximal number of address tokens are allowed in an address message
2290 header. Information that exceeds the limit is discarded. The limit is
2291 enforced by the cleanup(8) server.
2292
2294 Optional lookup tables for content inspection of primary non-MIME mes‐
2295 sage headers, as specified in the header_checks(5) manual page.
2296
2298 The format of the Postfix-generated From: header. This setting affects
2299 the appearance of 'full name' information when a local program such as
2300 /bin/mail submits a message without From: header through the Postfix
2301 sendmail(1) command.
2302 Specify one of the following:
2304 standard (default)
2306 Produce a header formatted as "From: name <address>". This is
2307 the default as of Postfix 3.3.
2308 obsolete
2310 Produce a header formatted as "From: address (name)". This is
2311 the behavior prior to Postfix 3.3.
2312 Notes:
2314 • Postfix generates the format "From: address" when name informa‐
2316 tion is unavailable or the envelope sender address is empty.
2317 This is the same behavior as prior to Postfix 3.3.
2318 • In the standard form, the name will be quoted if it contains
2320 specials as defined in RFC 5322, or the "!%" address operators.
2321 • The Postfix sendmail(1) command gets name information from the
2323 -F command-line option, from the NAME environment variable, or
2324 from the UNIX password file.
2325 This feature is available in Postfix 3.3 and later.
2327
2329 The maximal amount of memory in bytes for storing a message header. If
2330 a header is larger, the excess is discarded. The limit is enforced by
2331 the cleanup(8) server.
2332
2334 Log warnings about problematic configuration settings, and provide
2335 helpful suggestions.
2336 This feature is available in Postfix 2.0 and later.
2338
2340 Optional pathname of a mailbox file relative to a local(8) user's home
2341 directory.
2342 Specify a pathname ending in "/" for qmail-style delivery.
2344 The precedence of local(8) delivery features from high to low is:
2346 aliases, .forward files, mailbox_transport_maps, mailbox_transport,
2347 mailbox_command_maps, mailbox_command, home_mailbox, mail_spool_direc‐
2348 tory, fallback_transport_maps, fallback_transport and luser_relay.
2349 Examples:
2351 home_mailbox = Mailbox
2353 home_mailbox = Maildir/
2354
2356 The maximal number of Received: message headers that is allowed in the
2357 primary message headers. A message that exceeds the limit is bounced,
2358 in order to stop a mailer loop.
2359
2361 The location of Postfix HTML files that describe how to build, config‐
2362 ure or operate a specific Postfix subsystem or feature.
2363
2365 Ignore DNS MX lookups that produce no response. By default, the Post‐
2366 fix SMTP client defers delivery and tries again after some delay. This
2367 behavior is required by the SMTP standard.
2368 Specify "ignore_mx_lookup_error = yes" to force a DNS A record lookup
2370 instead. This violates the SMTP standard and can result in mis-delivery
2371 of mail.
2372
2374 The list of environment parameters that a privileged Postfix process
2375 will import from a non-Postfix parent process, or name=value environ‐
2376 ment overrides. Unprivileged utilities will enforce the name=value
2377 overrides, but otherwise will not change their process environment.
2378 Examples of relevant parameters:
2379 TZ May be needed for sane time keeping on most System-V-ish sys‐
2381 tems.
2382 DISPLAY
2384 Needed for debugging Postfix daemons with an X-windows debugger.
2385 XAUTHORITY
2387 Needed for debugging Postfix daemons with an X-windows debugger.
2388 MAIL_CONFIG
2390 Needed to make "postfix -c" work.
2391 Specify a list of names and/or name=value pairs, separated by white‐
2393 space or comma. Specify "{ name=value }" to protect whitespace or comma
2394 in parameter values (whitespace after the opening "{" and before the
2395 closing "}" is ignored). The form name=value is supported with Postfix
2396 version 2.1 and later; the use of {} is supported with Postfix 3.0 and
2397 later.
2398
2400 Time to pause before accepting a new message, when the message arrival
2401 rate exceeds the message delivery rate. This feature is turned on by
2402 default (it's disabled on SCO UNIX due to an SCO bug).
2403 With the default 100 Postfix SMTP server process limit, "in_flow_delay
2405 = 1s" limits the mail inflow to 100 messages per second above the num‐
2406 ber of messages delivered per second.
2407 Specify 0 to disable the feature. Valid delays are 0..10.
2409
2411 The network interface addresses that this mail system receives mail on.
2412 Specify "all" to receive mail on all network interfaces (default), and
2413 "loopback-only" to receive mail on loopback network interfaces only
2414 (Postfix version 2.2 and later). The parameter also controls delivery
2415 of mail to user@[ip.address].
2416 Note 1: you need to stop and start Postfix when this parameter changes.
2418 Note 2: address information may be enclosed inside [], but this form is
2420 not required here.
2421 When inet_interfaces specifies just one IPv4 and/or IPv6 address that
2423 is not a loopback address, the Postfix SMTP client will use this ad‐
2424 dress as the IP source address for outbound mail. Support for IPv6 is
2425 available in Postfix version 2.2 and later.
2426 On a multi-homed firewall with separate Postfix instances listening on
2428 the "inside" and "outside" interfaces, this can prevent each instance
2429 from being able to reach remote SMTP servers on the "other side" of the
2430 firewall. Setting smtp_bind_address to 0.0.0.0 avoids the potential
2431 problem for IPv4, and setting smtp_bind_address6 to :: solves the prob‐
2432 lem for IPv6.
2433 A better solution for multi-homed firewalls is to leave inet_interfaces
2435 at the default value and instead use explicit IP addresses in the mas‐
2436 ter.cf SMTP server definitions. This preserves the Postfix SMTP
2437 client's loop detection, by ensuring that each side of the firewall
2438 knows that the other IP address is still the same host. Setting
2439 $inet_interfaces to a single IPv4 and/or IPV6 address is primarily use‐
2440 ful with virtual hosting of domains on secondary IP addresses, when
2441 each IP address serves a different domain (and has a different $myhost‐
2442 name setting).
2443 See also the proxy_interfaces parameter, for network addresses that are
2445 forwarded to Postfix by way of a proxy or address translator.
2446 Examples:
2448 inet_interfaces = all (DEFAULT)
2450 inet_interfaces = loopback-only (Postfix version 2.2 and later)
2451 inet_interfaces = 127.0.0.1
2452 inet_interfaces = 127.0.0.1, [::1] (Postfix version 2.2 and later)
2453 inet_interfaces = 192.168.1.2, 127.0.0.1
2454
2456 The Internet protocols Postfix will attempt to use when making or ac‐
2457 cepting connections. Specify one or more of "ipv4" or "ipv6", separated
2458 by whitespace or commas. The form "all" is equivalent to "ipv4, ipv6"
2459 or "ipv4", depending on whether the operating system implements IPv6.
2460 With Postfix 2.8 and earlier the default is "ipv4". For backwards com‐
2462 patibility with these releases, the Postfix 2.9 and later upgrade pro‐
2463 cedure appends an explicit "inet_protocols = ipv4" setting to main.cf
2464 when no explicit setting is present. This compatibility workaround will
2465 be phased out as IPv6 deployment becomes more common.
2466 This feature is available in Postfix 2.2 and later.
2468 Note: you MUST stop and start Postfix after changing this parameter.
2470 On systems that pre-date IPV6_V6ONLY support (RFC 3493), an IPv6 server
2472 will also accept IPv4 connections, even when IPv4 is turned off with
2473 the inet_protocols parameter. On systems with IPV6_V6ONLY support,
2474 Postfix will use separate server sockets for IPv6 and IPv4, and each
2475 will accept only connections for the corresponding protocol.
2476 When IPv4 support is enabled via the inet_protocols parameter, Postfix
2478 will look up DNS type A records, and will convert IPv4-in-IPv6 client
2479 IP addresses (::ffff:1.2.3.4) to their original IPv4 form (1.2.3.4).
2480 The latter is needed on hosts that pre-date IPV6_V6ONLY support (RFC
2481 3493).
2482 When IPv6 support is enabled via the inet_protocols parameter, Postfix
2484 will do DNS type AAAA record lookups.
2485 When both IPv4 and IPv6 support are enabled, the Postfix SMTP client
2487 will choose the protocol as specified with the smtp_address_preference
2488 parameter. Postfix versions before 2.8 attempt to connect via IPv6 be‐
2489 fore attempting to use IPv4.
2490 Examples:
2492 inet_protocols = ipv4
2494 inet_protocols = all (DEFAULT)
2495 inet_protocols = ipv6
2496 inet_protocols = ipv4, ipv6
2497
2499 The email address form that will be used in non-debug logging (info,
2500 warning, etc.). As of Postfix 3.5 when an address localpart contains
2501 spaces or other special characters, the localpart will be quoted, for
2502 example:
2503 from=<"name with spaces"@example.com>
2505 Older Postfix versions would log the internal (unquoted) form:
2507 from=<name with spaces@example.com>
2509 The external and internal forms are identical for the vast majority of
2511 email addresses that contain no spaces or other special characters in
2512 the localpart.
2513 The logging in external form is consistent with the address form that
2515 Postfix 3.2 and later prefer for most table lookups. This is therefore
2516 the more useful form for non-debug logging.
2517 Specify "info_log_address_format = internal" for backwards compatibil‐
2519 ity.
2520 Postfix uses the unquoted form internally, because an attacker can
2522 specify an email address in different forms by playing games with
2523 quotes and backslashes. An attacker should not be able to use such
2524 games to circumvent Postfix access policies.
2525 This feature is available in Postfix 3.5 and later.
2527
2529 The initial per-destination concurrency level for parallel delivery to
2530 the same destination. With per-destination recipient limit > 1, a des‐
2531 tination is a domain, otherwise it is a recipient.
2532 Use transport_initial_destination_concurrency to specify a trans‐
2534 port-specific override, where transport is the master.cf name of the
2535 message delivery transport (Postfix 2.5 and later).
2536 Warning: with concurrency of 1, one bad message can be enough to block
2538 all mail to a site.
2539
2541 What categories of Postfix-generated mail are subject to before-queue
2542 content inspection by non_smtpd_milters, header_checks and body_checks.
2543 Specify zero or more of the following, separated by whitespace or
2544 comma.
2545 bounce Inspect the content of delivery status notifications.
2547 notify Inspect the content of postmaster notifications by the smtp(8)
2549 and smtpd(8) processes.
2550 NOTE: It's generally not safe to enable content inspection of Post‐
2552 fix-generated email messages. The user is warned.
2553 This feature is available in Postfix 2.3 and later.
2555
2557 The numerical Postfix SMTP server response code when the client HELO or
2558 EHLO command parameter is rejected by the reject_invalid_helo_hostname
2559 restriction.
2560 Do not change this unless you have a complete understanding of RFC
2562 5321.
2563
2565 The time after which a client closes an idle internal communication
2566 channel. The purpose is to allow Postfix daemon processes to terminate
2567 voluntarily after they become idle. This is used, for example, by the
2568 Postfix address resolving and rewriting clients.
2569 With Postfix 2.4 the default value was reduced from 100s to 5s.
2571 Time units: s (seconds), m (minutes), h (hours), d (days), w (weeks).
2573 The default time unit is s (seconds).
2574
2576 The time limit for sending or receiving information over an internal
2577 communication channel. The purpose is to break out of deadlock situa‐
2578 tions. If the time limit is exceeded the software aborts with a fatal
2579 error.
2580 Time units: s (seconds), m (minutes), h (hours), d (days), w (weeks).
2582 The default time unit is s (seconds).
2583
2585 The time after which a client closes an active internal communication
2586 channel. The purpose is to allow Postfix daemon processes to terminate
2587 voluntarily after reaching their client limit. This is used, for exam‐
2588 ple, by the Postfix address resolving and rewriting clients.
2589 Time units: s (seconds), m (minutes), h (hours), d (days), w (weeks).
2591 The default time unit is s (seconds).
2592 This feature is available in Postfix 2.1 and later.
2594
2596 sion=587)
2597 Optional setting that avoids lookups in the services(5) database. This
2598 feature was implemented to address inconsistencies in the name of the
2599 port "465" service. The ABNF is:
2600 known_tcp_ports = empty | name-to-port *("," name-to-port)
2602 name-to-port = 1*(service-name "=') port-number
2603 Whitespace is optional but it cannot appear inside a service name or
2605 port number.
2606 This feature is available in Postfix 3.6 and later.
2608
2610 Upon input, long lines are chopped up into pieces of at most this
2611 length; upon delivery, long lines are reconstructed.
2612
2614 The initial OpenLDAP LMDB database size limit in bytes. Each time a
2615 database becomes full, its size limit is doubled.
2616 This feature is available in Postfix 2.11 and later.
2618
2620 The LMTP-specific version of the smtp_address_preference configuration
2621 parameter. See there for details.
2622 This feature is available in Postfix 2.8 and later.
2624
2626 The LMTP-specific version of the smtp_address_verify_target configura‐
2627 tion parameter. See there for details.
2628 This feature is available in Postfix 3.0 and later.
2630
2632 When a remote LMTP server announces no DSN support, assume that the
2633 server performs final delivery, and send "delivered" delivery status
2634 notifications instead of "relayed". The default setting is backwards
2635 compatible to avoid the infinitesimal possibility of breaking existing
2636 LMTP-based content filters.
2637
2639 The LMTP-specific version of the smtp_balance_inet_protocols configura‐
2640 tion parameter. See there for details.
2641 This feature is available in Postfix 3.3 and later.
2643
2645 The LMTP-specific version of the smtp_bind_address configuration param‐
2646 eter. See there for details.
2647 This feature is available in Postfix 2.3 and later.
2649
2651 The LMTP-specific version of the smtp_bind_address6 configuration pa‐
2652 rameter. See there for details.
2653 This feature is available in Postfix 2.3 and later.
2655
2657 The LMTP-specific version of the smtp_body_checks configuration parame‐
2658 ter. See there for details.
2659 This feature is available in Postfix 2.5 and later.
2661
2663 Keep Postfix LMTP client connections open for up to $max_idle seconds.
2664 When the LMTP client receives a request for the same connection the
2665 connection is reused.
2666 This parameter is available in Postfix version 2.2 and earlier. With
2668 Postfix version 2.3 and later, see lmtp_connection_cache_on_demand,
2669 lmtp_connection_cache_destinations, or lmtp_connection_re‐
2670 use_time_limit.
2671 The effectiveness of cached connections will be determined by the num‐
2673 ber of remote LMTP servers in use, and the concurrency limit specified
2674 for the Postfix LMTP client. Cached connections are closed under any of
2675 the following conditions:
2676 • The Postfix LMTP client idle time limit is reached. This limit
2678 is specified with the Postfix max_idle configuration parameter.
2679 • A delivery request specifies a different destination than the
2681 one currently cached.
2682 • The per-process limit on the number of delivery requests is
2684 reached. This limit is specified with the Postfix max_use con‐
2685 figuration parameter.
2686 • Upon the onset of another delivery request, the remote LMTP
2688 server associated with the current session does not respond to
2689 the RSET command.
2690 Most of these limitations have been with the Postfix a connection cache
2692 that is shared among multiple LMTP client programs.
2693
2695 The LMTP-specific version of the smtp_cname_overrides_servername con‐
2696 figuration parameter. See there for details.
2697 This feature is available in Postfix 2.3 and later.
2699
2701 The Postfix LMTP client time limit for completing a TCP connection, or
2702 zero (use the operating system built-in time limit). When no connec‐
2703 tion can be made within the deadline, the LMTP client tries the next
2704 address on the mail exchanger list.
2705 Time units: s (seconds), m (minutes), h (hours), d (days), w (weeks).
2707 The default time unit is s (seconds).
2708 Example:
2710 lmtp_connect_timeout = 30s
2712
2714 The LMTP-specific version of the smtp_connection_cache_destinations
2715 configuration parameter. See there for details.
2716 This feature is available in Postfix 2.3 and later.
2718
2720 The LMTP-specific version of the smtp_connection_cache_on_demand con‐
2721 figuration parameter. See there for details.
2722 This feature is available in Postfix 2.3 and later.
2724
2726 The LMTP-specific version of the smtp_connection_cache_time_limit con‐
2727 figuration parameter. See there for details.
2728 This feature is available in Postfix 2.3 and later.
2730
2732 The LMTP-specific version of the smtp_connection_reuse_count_limit con‐
2733 figuration parameter. See there for details.
2734 This feature is available in Postfix 2.11 and later.
2736
2738 The LMTP-specific version of the smtp_connection_reuse_time_limit con‐
2739 figuration parameter. See there for details.
2740 This feature is available in Postfix 2.3 and later.
2742
2744 The Postfix LMTP client time limit for sending the LMTP ".", and for
2745 receiving the remote LMTP server response. When no response is re‐
2746 ceived within the deadline, a warning is logged that the mail may be
2747 delivered multiple times.
2748 Time units: s (seconds), m (minutes), h (hours), d (days), w (weeks).
2750 The default time unit is s (seconds).
2751
2753 The Postfix LMTP client time limit for sending the LMTP DATA command,
2754 and for receiving the remote LMTP server response.
2755 Time units: s (seconds), m (minutes), h (hours), d (days), w (weeks).
2757 The default time unit is s (seconds).
2758
2760 The Postfix LMTP client time limit for sending the LMTP message con‐
2761 tent. When the connection stalls for more than $lmtp_data_xfer_timeout
2762 the LMTP client terminates the transfer.
2763 Time units: s (seconds), m (minutes), h (hours), d (days), w (weeks).
2765 The default time unit is s (seconds).
2766
2768 The LMTP-specific version of the smtp_defer_if_no_mx_address_found con‐
2769 figuration parameter. See there for details.
2770 This feature is available in Postfix 2.3 and later.
2772
2774 The LMTP-specific version of the smtp_delivery_status_filter configura‐
2775 tion parameter. See there for details.
2776 This feature is available in Postfix 3.0 and later.
2778
2780 rency_limit)
2781 The maximal number of parallel deliveries to the same destination via
2782 the lmtp message delivery transport. This limit is enforced by the
2783 queue manager. The message delivery transport name is the first field
2784 in the entry in the master.cf file.
2785
2787 ent_limit)
2788 The maximal number of recipients per message for the lmtp message de‐
2789 livery transport. This limit is enforced by the queue manager. The mes‐
2790 sage delivery transport name is the first field in the entry in the
2791 master.cf file.
2792 Setting this parameter to a value of 1 changes the meaning of lmtp_des‐
2794 tination_concurrency_limit from concurrency per domain into concurrency
2795 per recipient.
2796
2798 Lookup tables, indexed by the remote LMTP server address, with case in‐
2799 sensitive lists of LHLO keywords (pipelining, starttls, auth, etc.)
2800 that the Postfix LMTP client will ignore in the LHLO response from a
2801 remote LMTP server. See lmtp_discard_lhlo_keywords for details. The ta‐
2802 ble is not indexed by hostname for consistency with smtpd_dis‐
2803 card_ehlo_keyword_address_maps.
2804 This feature is available in Postfix 2.3 and later.
2806
2808 A case insensitive list of LHLO keywords (pipelining, starttls, auth,
2809 etc.) that the Postfix LMTP client will ignore in the LHLO response
2810 from a remote LMTP server.
2811 This feature is available in Postfix 2.3 and later.
2813 Notes:
2815 • Specify the silent-discard pseudo keyword to prevent this action
2817 from being logged.
2818 • Use the lmtp_discard_lhlo_keyword_address_maps feature to dis‐
2820 card LHLO keywords selectively.
2821
2823 Optional filter for Postfix LMTP client DNS lookup results. See
2824 smtp_dns_reply_filter for details including an example.
2825 This feature is available in Postfix 3.0 and later.
2827
2829 The LMTP-specific version of the smtp_dns_resolver_options configura‐
2830 tion parameter. See there for details.
2831 This feature is available in Postfix 2.8 and later.
2833
2835 The LMTP-specific version of the smtp_dns_support_level configuration
2836 parameter. See there for details.
2837 This feature is available in Postfix 2.11 and later.
2839
2841 The LMTP-specific version of the smtp_enforce_tls configuration parame‐
2842 ter. See there for details.
2843 This feature is available in Postfix 2.3 and later.
2845
2847 Optional list of relay hosts for LMTP destinations that can't be found
2848 or that are unreachable. In main.cf elements are separated by white‐
2849 space or commas.
2850 By default, mail is returned to the sender when a destination is not
2852 found, and delivery is deferred when a destination is unreachable.
2853 The fallback relays must be TCP destinations, specified without a lead‐
2855 ing "inet:" prefix. Specify a host or host:port. Since MX lookups do
2856 not apply with LMTP, there is no need to use the "[host]" or
2857 "[host]:port" forms. If you specify multiple LMTP destinations, Post‐
2858 fix will try them in the specified order.
2859 This feature is available in Postfix 3.1 and later.
2861
2863 The LMTP-specific version of the smtp_generic_maps configuration param‐
2864 eter. See there for details.
2865 This feature is available in Postfix 2.3 and later.
2867
2869 The LMTP-specific version of the smtp_header_checks configuration pa‐
2870 rameter. See there for details.
2871 This feature is available in Postfix 2.5 and later.
2873
2875 The LMTP-specific version of the smtp_host_lookup configuration parame‐
2876 ter. See there for details.
2877 This feature is available in Postfix 2.3 and later.
2879
2881 The hostname to send in the LMTP LHLO command.
2882 The default value is the machine hostname. Specify a hostname or
2884 [ip.add.re.ss].
2885 This information can be specified in the main.cf file for all LMTP
2887 clients, or it can be specified in the master.cf file for a specific
2888 client, for example:
2889 /etc/postfix/master.cf:
2891 mylmtp ... lmtp -o lmtp_lhlo_name=foo.bar.com
2892 This feature is available in Postfix 2.3 and later.
2894
2896 The Postfix LMTP client time limit for sending the LHLO command, and
2897 for receiving the initial remote LMTP server response.
2898 Time units: s (seconds), m (minutes), h (hours), d (days), w (weeks).
2900 The default time unit is s (seconds).
2901
2903 The LMTP-specific version of the smtp_line_length_limit configuration
2904 parameter. See there for details.
2905 This feature is available in Postfix 2.3 and later.
2907
2909 The Postfix LMTP client time limit for sending the MAIL FROM command,
2910 and for receiving the remote LMTP server response.
2911 Time units: s (seconds), m (minutes), h (hours), d (days), w (weeks).
2913 The default time unit is s (seconds).
2914
2916 The LMTP-specific version of the smtp_mime_header_checks configuration
2917 parameter. See there for details.
2918 This feature is available in Postfix 2.5 and later.
2920
2922 The LMTP-specific version of the smtp_mx_address_limit configuration
2923 parameter. See there for details.
2924 This feature is available in Postfix 2.3 and later.
2926
2928 The LMTP-specific version of the smtp_mx_session_limit configuration
2929 parameter. See there for details.
2930 This feature is available in Postfix 2.3 and later.
2932
2934 The LMTP-specific version of the smtp_nested_header_checks configura‐
2935 tion parameter. See there for details.
2936 This feature is available in Postfix 2.5 and later.
2938
2940 The LMTP-specific version of the smtp_per_record_deadline configuration
2941 parameter. See there for details.
2942 This feature is available in Postfix 2.9 and later.
2944
2946 The LMTP-specific version of the smtp_pix_workaround_delay_time config‐
2947 uration parameter. See there for details.
2948 This feature is available in Postfix 2.3 and later.
2950
2952 The LMTP-specific version of the smtp_pix_workaround_maps configuration
2953 parameter. See there for details.
2954 This feature is available in Postfix 2.4 and later.
2956
2958 The LMTP-specific version of the smtp_pix_workaround_threshold_time
2959 configuration parameter. See there for details.
2960 This feature is available in Postfix 2.3 and later.
2962
2964 The LMTP-specific version of the smtp_pix_workaround configuration pa‐
2965 rameter. See there for details.
2966 This feature is available in Postfix 2.4 and later.
2968
2970 The Postfix LMTP client time limit for sending the QUIT command, and
2971 for receiving the remote LMTP server response.
2972 Time units: s (seconds), m (minutes), h (hours), d (days), w (weeks).
2974 The default time unit is s (seconds).
2975
2977 The LMTP-specific version of the smtp_quote_rfc821_envelope configura‐
2978 tion parameter. See there for details.
2979 This feature is available in Postfix 2.3 and later.
2981
2983 The LMTP-specific version of the smtp_randomize_addresses configuration
2984 parameter. See there for details.
2985 This feature is available in Postfix 2.3 and later.
2987
2989 The Postfix LMTP client time limit for sending the RCPT TO command, and
2990 for receiving the remote LMTP server response.
2991 Time units: s (seconds), m (minutes), h (hours), d (days), w (weeks).
2993 The default time unit is s (seconds).
2994
2996 The LMTP-specific version of the smtp_reply_filter configuration param‐
2997 eter. See there for details.
2998 This feature is available in Postfix 2.7 and later.
3000
3002 The Postfix LMTP client time limit for sending the RSET command, and
3003 for receiving the remote LMTP server response. The LMTP client sends
3004 RSET in order to finish a recipient address probe, or to verify that a
3005 cached connection is still alive.
3006 Time units: s (seconds), m (minutes), h (hours), d (days), w (weeks).
3008 The default time unit is s (seconds).
3009
3011 The LMTP-specific version of the smtp_sasl_auth_cache_name configura‐
3012 tion parameter. See there for details.
3013 This feature is available in Postfix 2.5 and later.
3015
3017 The LMTP-specific version of the smtp_sasl_auth_cache_time configura‐
3018 tion parameter. See there for details.
3019 This feature is available in Postfix 2.5 and later.
3021
3023 Enable SASL authentication in the Postfix LMTP client.
3024
3026 The LMTP-specific version of the smtp_sasl_auth_soft_bounce configura‐
3027 tion parameter. See there for details.
3028 This feature is available in Postfix 2.5 and later.
3030
3032 The LMTP-specific version of the smtp_sasl_mechanism_filter configura‐
3033 tion parameter. See there for details.
3034 This feature is available in Postfix 2.3 and later.
3036
3038 Optional Postfix LMTP client lookup tables with one username:password
3039 entry per host or domain. If a remote host or domain has no user‐
3040 name:password entry, then the Postfix LMTP client will not attempt to
3041 authenticate to the remote host.
3042
3044 Implementation-specific information that is passed through to the SASL
3045 plug-in implementation that is selected with lmtp_sasl_type. Typically
3046 this specifies the name of a configuration file or rendezvous point.
3047 This feature is available in Postfix 2.3 and later.
3049
3051 SASL security options; as of Postfix 2.3 the list of available features
3052 depends on the SASL client implementation that is selected with
3053 lmtp_sasl_type.
3054 The following security features are defined for the cyrus client SASL
3056 implementation:
3057 noplaintext
3059 Disallow authentication methods that use plaintext passwords.
3060 noactive
3062 Disallow authentication methods that are vulnerable to non-dic‐
3063 tionary active attacks.
3064 nodictionary
3066 Disallow authentication methods that are vulnerable to passive
3067 dictionary attack.
3068 noanonymous
3070 Disallow anonymous logins.
3071 Example:
3073 lmtp_sasl_security_options = noplaintext
3075
3077 The LMTP-specific version of the smtp_sasl_tls_security_options config‐
3078 uration parameter. See there for details.
3079 This feature is available in Postfix 2.3 and later.
3081
3083 tions)
3084 The LMTP-specific version of the smtp_sasl_tls_verified_security_op‐
3085 tions configuration parameter. See there for details.
3086 This feature is available in Postfix 2.3 and later.
3088
3090 The SASL plug-in type that the Postfix LMTP client should use for au‐
3091 thentication. The available types are listed with the "postconf -A"
3092 command.
3093 This feature is available in Postfix 2.3 and later.
3095
3097 The LMTP-specific version of the smtp_send_dummy_mail_auth configura‐
3098 tion parameter. See there for details.
3099 This feature is available in Postfix 2.9 and later.
3101
3103 Send an XFORWARD command to the remote LMTP server when the LMTP LHLO
3104 server response announces XFORWARD support. This allows an lmtp(8) de‐
3105 livery agent, used for content filter message injection, to forward the
3106 name, address, protocol and HELO name of the original client to the
3107 content filter and downstream queuing LMTP server. Before you change
3108 the value to yes, it is best to make sure that your content filter sup‐
3109 ports this command.
3110 This feature is available in Postfix 2.1 and later.
3112
3114 The LMTP-specific version of the smtp_sender_dependent_authentication
3115 configuration parameter. See there for details.
3116 This feature is available in Postfix 2.3 and later.
3118
3120 The LMTP-specific version of the smtp_skip_5xx_greeting configuration
3121 parameter. See there for details.
3122 This feature is available in Postfix 2.3 and later.
3124
3126 Wait for the response to the LMTP QUIT command.
3127
3129 The LMTP-specific version of the smtp_starttls_timeout configuration
3130 parameter. See there for details.
3131 This feature is available in Postfix 2.3 and later.
3133
3135 The default TCP port that the Postfix LMTP client connects to. Specify
3136 a symbolic name (see services(5)) or a numeric port.
3137
3139 The LMTP-specific version of the smtp_tls_CAfile configuration parame‐
3140 ter. See there for details.
3141 This feature is available in Postfix 2.3 and later.
3143
3145 The LMTP-specific version of the smtp_tls_CApath configuration parame‐
3146 ter. See there for details.
3147 This feature is available in Postfix 2.3 and later.
3149
3151 The LMTP-specific version of the smtp_tls_block_early_mail_reply con‐
3152 figuration parameter. See there for details.
3153 This feature is available in Postfix 2.7 and later.
3155
3157 The LMTP-specific version of the smtp_tls_cert_file configuration pa‐
3158 rameter. See there for details.
3159 This feature is available in Postfix 2.3 and later.
3161
3163 The LMTP-specific version of the smtp_tls_chain_files configuration pa‐
3164 rameter. See there for details.
3165 This feature is available in Postfix 3.4 and later.
3167
3169 The LMTP-specific version of the smtp_tls_ciphers configuration parame‐
3170 ter. See there for details.
3171 This feature is available in Postfix 2.6 and later.
3173
3175 The LMTP-specific version of the smtp_tls_connection_reuse configura‐
3176 tion parameter. See there for details.
3177 This feature is available in Postfix 3.4 and later.
3179
3181 The LMTP-specific version of the smtp_tls_dcert_file configuration pa‐
3182 rameter. See there for details.
3183 This feature is available in Postfix 2.3 and later.
3185
3187 The LMTP-specific version of the smtp_tls_dkey_file configuration pa‐
3188 rameter. See there for details.
3189 This feature is available in Postfix 2.3 and later.
3191
3193 The LMTP-specific version of the smtp_tls_eccert_file configuration pa‐
3194 rameter. See there for details.
3195 This feature is available in Postfix 2.6 and later, when Postfix is
3197 compiled and linked with OpenSSL 1.0.0 or later.
3198
3200 The LMTP-specific version of the smtp_tls_eckey_file configuration pa‐
3201 rameter. See there for details.
3202 This feature is available in Postfix 2.6 and later, when Postfix is
3204 compiled and linked with OpenSSL 1.0.0 or later.
3205
3207 The LMTP-specific version of the smtp_tls_enforce_peername configura‐
3208 tion parameter. See there for details.
3209 This feature is available in Postfix 2.3 and later.
3211
3213 The LMTP-specific version of the smtp_tls_exclude_ciphers configuration
3214 parameter. See there for details.
3215 This feature is available in Postfix 2.3 and later.
3217
3219 The LMTP-specific version of the smtp_tls_fingerprint_cert_match con‐
3220 figuration parameter. See there for details.
3221 This feature is available in Postfix 2.5 and later.
3223
3225 The LMTP-specific version of the smtp_tls_fingerprint_digest configura‐
3226 tion parameter. See there for details.
3227 This feature is available in Postfix 2.5 and later.
3229
3231 The LMTP-specific version of the smtp_tls_force_inse‐
3232 cure_host_tlsa_lookup configuration parameter. See there for details.
3233 This feature is available in Postfix 2.11 and later.
3235
3237 The LMTP-specific version of the smtp_tls_key_file configuration param‐
3238 eter. See there for details.
3239 This feature is available in Postfix 2.3 and later.
3241
3243 The LMTP-specific version of the smtp_tls_loglevel configuration param‐
3244 eter. See there for details.
3245 This feature is available in Postfix 2.3 and later.
3247
3249 The LMTP-specific version of the smtp_tls_mandatory_ciphers configura‐
3250 tion parameter. See there for details.
3251 This feature is available in Postfix 2.3 and later.
3253
3255 The LMTP-specific version of the smtp_tls_mandatory_exclude_ciphers
3256 configuration parameter. See there for details.
3257 This feature is available in Postfix 2.3 and later.
3259
3261 The LMTP-specific version of the smtp_tls_mandatory_protocols configu‐
3262 ration parameter. See there for details.
3263 This feature is available in Postfix 2.3 and later.
3265
3267 The LMTP-specific version of the smtp_tls_note_starttls_offer configu‐
3268 ration parameter. See there for details.
3269 This feature is available in Postfix 2.3 and later.
3271
3273 The LMTP-specific version of the smtp_tls_per_site configuration param‐
3274 eter. See there for details.
3275 This feature is available in Postfix 2.3 and later.
3277
3279 The LMTP-specific version of the smtp_tls_policy_maps configuration pa‐
3280 rameter. See there for details.
3281 This feature is available in Postfix 2.3 and later.
3283
3285 The LMTP-specific version of the smtp_tls_protocols configuration pa‐
3286 rameter. See there for details.
3287 This feature is available in Postfix 2.6 and later.
3289
3291 The LMTP-specific version of the smtp_tls_scert_verifydepth configura‐
3292 tion parameter. See there for details.
3293 This feature is available in Postfix 2.3 and later.
3295
3297 The LMTP-specific version of the smtp_tls_secure_cert_match configura‐
3298 tion parameter. See there for details.
3299 This feature is available in Postfix 2.3 and later.
3301
3303 The LMTP-specific version of the smtp_tls_security_level configuration
3304 parameter. See there for details.
3305 This feature is available in Postfix 2.3 and later.
3307
3309 The LMTP-specific version of the smtp_tls_servername configuration pa‐
3310 rameter. See there for details.
3311 This feature is available in Postfix 3.4 and later.
3313
3315 The LMTP-specific version of the smtp_tls_session_cache_database con‐
3316 figuration parameter. See there for details.
3317 This feature is available in Postfix 2.3 and later.
3319
3321 The LMTP-specific version of the smtp_tls_session_cache_timeout config‐
3322 uration parameter. See there for details.
3323 This feature is available in Postfix 2.3 and later.
3325
3327 The LMTP-specific version of the smtp_tls_trust_anchor_file configura‐
3328 tion parameter. See there for details.
3329 This feature is available in Postfix 2.11 and later.
3331
3333 The LMTP-specific version of the smtp_tls_verify_cert_match configura‐
3334 tion parameter. See there for details.
3335 This feature is available in Postfix 2.3 and later.
3337
3339 The LMTP-specific version of the smtp_use_tls configuration parameter.
3340 See there for details.
3341 This feature is available in Postfix 2.3 and later.
3343
3345 The Postfix LMTP client time limit for sending the XFORWARD command,
3346 and for receiving the remote LMTP server response.
3347 In case of problems the client does NOT try the next address on the
3349 mail exchanger list.
3350 Time units: s (seconds), m (minutes), h (hours), d (days), w (weeks).
3352 The default time unit is s (seconds).
3353 This feature is available in Postfix 2.1 and later.
3355
3357 Optional shell program for local(8) delivery to non-Postfix command.
3358 By default, non-Postfix commands are executed directly; commands are
3359 given to given to the default shell (typically, /bin/sh) only when they
3360 contain shell meta characters or shell built-in commands.
3361 "sendmail's restricted shell" (smrsh) is what most people will use in
3363 order to restrict what programs can be run from e.g. .forward files
3364 (smrsh is part of the Sendmail distribution).
3365 Note: when a shell program is specified, it is invoked even when the
3367 command contains no shell built-in commands or meta characters.
3368 Example:
3370 local_command_shell = /some/where/smrsh -c
3372 local_command_shell = /bin/bash -c
3373
3375 Optional filter for the local(8) delivery agent to change the status
3376 code or explanatory text of successful or unsuccessful deliveries. See
3377 default_delivery_status_filter for details.
3378 This feature is available in Postfix 3.0 and later.
3380
3382 The maximal number of parallel deliveries via the local mail delivery
3383 transport to the same recipient (when "local_destination_recipi‐
3384 ent_limit = 1") or the maximal number of parallel deliveries to the
3385 same local domain (when "local_destination_recipient_limit > 1"). This
3386 limit is enforced by the queue manager. The message delivery transport
3387 name is the first field in the entry in the master.cf file.
3388 A low limit of 2 is recommended, just in case someone has an expensive
3390 shell command in a .forward file or in an alias (e.g., a mailing list
3391 manager). You don't want to run lots of those at the same time.
3392
3394 The maximal number of recipients per message delivery via the local
3395 mail delivery transport. This limit is enforced by the queue manager.
3396 The message delivery transport name is the first field in the entry in
3397 the master.cf file.
3398 Setting this parameter to a value > 1 changes the meaning of local_des‐
3400 tination_concurrency_limit from concurrency per recipient into concur‐
3401 rency per domain.
3402
3404 Rewrite message header addresses in mail from these clients and update
3405 incomplete addresses with the domain name in $myorigin or $mydomain;
3406 either don't rewrite message headers from other clients at all, or re‐
3407 write message headers and update incomplete addresses with the domain
3408 specified in the remote_header_rewrite_domain parameter.
3409 See the append_at_myorigin and append_dot_mydomain parameters for de‐
3411 tails of how domain names are appended to incomplete addresses.
3412 Specify a list of zero or more of the following:
3414 permit_inet_interfaces
3416 Append the domain name in $myorigin or $mydomain when the client
3417 IP address matches $inet_interfaces. This is enabled by default.
3418 permit_mynetworks
3420 Append the domain name in $myorigin or $mydomain when the client
3421 IP address matches any network or network address listed in
3422 $mynetworks. This setting will not prevent remote mail header
3423 address rewriting when mail from a remote client is forwarded by
3424 a neighboring system.
3425 permit_sasl_authenticated
3427 Append the domain name in $myorigin or $mydomain when the client
3428 is successfully authenticated via the RFC 4954 (AUTH) protocol.
3429 permit_tls_clientcerts
3431 Append the domain name in $myorigin or $mydomain when the remote
3432 SMTP client TLS certificate fingerprint or public key finger‐
3433 print (Postfix 2.9 and later) is listed in $relay_clientcerts.
3434 The fingerprint digest algorithm is configurable via the
3435 smtpd_tls_fingerprint_digest parameter (hard-coded as md5 prior
3436 to Postfix version 2.5).
3437 The default algorithm is sha256 with Postfix >= 3.6 and the com‐
3438 patibility_level set to 3.6 or higher. With Postfix <= 3.5, the
3439 default algorithm is md5. The best-practice algorithm is now
3440 sha256. Recent advances in hash function cryptanalysis have led
3441 to md5 and sha1 being deprecated in favor of sha256. However,
3442 as long as there are no known "second pre-image" attacks against
3443 the older algorithms, their use in this context, though not rec‐
3444 ommended, is still likely safe.
3445 permit_tls_all_clientcerts
3447 Append the domain name in $myorigin or $mydomain when the remote
3448 SMTP client TLS certificate is successfully verified, regardless
3449 of whether it is listed on the server, and regardless of the
3450 certifying authority.
3451 check_address_map type:table
3453 type:table
3455 Append the domain name in $myorigin or $mydomain when the client
3456 IP address matches the specified lookup table. The lookup re‐
3457 sult is ignored, and no subnet lookup is done. This is suitable
3458 for, e.g., pop-before-smtp lookup tables.
3459 Examples:
3461 The Postfix < 2.2 backwards compatible setting: always rewrite message
3463 headers, and always append my own domain to incomplete header ad‐
3464 dresses.
3465 local_header_rewrite_clients = static:all
3467 The purist (and default) setting: rewrite headers only in mail from
3469 Postfix sendmail and in SMTP mail from this machine.
3470 local_header_rewrite_clients = permit_inet_interfaces
3472 The intermediate setting: rewrite header addresses and append $myorigin
3474 or $mydomain information only with mail from Postfix sendmail, from lo‐
3475 cal clients, or from authorized SMTP clients.
3476 Note: this setting will not prevent remote mail header address rewrit‐
3478 ing when mail from a remote client is forwarded by a neighboring sys‐
3479 tem.
3480 local_header_rewrite_clients = permit_mynetworks,
3482 permit_sasl_authenticated permit_tls_clientcerts
3483 check_address_map hash:/etc/postfix/pop-before-smtp
3484
3486 A list of lookup tables that are searched by the UNIX login name, and
3487 that return a list of allowed envelope sender patterns separated by
3488 space or comma. These sender patterns are enforced by the Postfix post‐
3489 drop(1) command. The default is backwards-compatible: every user may
3490 specify any sender envelope address.
3491 When no UNIX login name is available, the postdrop(1) command will
3493 prepend "uid:" to the numerical UID and use that instead.
3494 This feature ignores address extensions in the user-specified envelope
3496 sender address.
3497 The following sender patterns are special; these cannot be used as part
3499 of a longer pattern.
3500 * This pattern allows any envelope sender address.
3502 <> This pattern allows the empty envelope sender address. See the
3504 empty_address_local_login_sender_maps_lookup_key configuration
3505 parameter.
3506 @domain
3508 This pattern allows an envelope sender address when the '@' and
3509 domain part match.
3510 Examples:
3512 /etc/postfix/main.cf:
3514 # Allow root and postfix full control, anyone else can only
3515 # send mail as themselves. Use "uid:" followed by the numerical
3516 # UID when the UID has no entry in the UNIX password file.
3517 local_login_sender_maps =
3518 inline:{ { root = *}, { postfix = * } },
3519 pcre:/etc/postfix/login_senders
3520 /etc/postfix/login_senders:
3522 # Allow both the bare username and the user@domain forms.
3523 /(.+)/ $1 $1@example.com/
3524 This feature is available in Postfix 3.6 and later.
3526
3528 Lookup tables with all names or addresses of local recipients: a recip‐
3529 ient address is local when its domain matches $mydestination, $inet_in‐
3530 terfaces or $proxy_interfaces. Specify @domain as a wild-card for do‐
3531 mains that do not have a valid recipient list. Technically, tables
3532 listed with $local_recipient_maps are used as lists: Postfix needs to
3533 know only if a lookup string is found or not, but it does not use the
3534 result from table lookup.
3535 Specify zero or more "type:name" lookup tables, separated by whitespace
3537 or comma. Tables will be searched in the specified order until a match
3538 is found.
3539 If this parameter is non-empty (the default), then the Postfix SMTP
3541 server will reject mail for unknown local users.
3542 To turn off local recipient checking in the Postfix SMTP server, spec‐
3544 ify "local_recipient_maps =" (i.e. empty).
3545 The default setting assumes that you use the default Postfix local de‐
3547 livery agent for local delivery. You need to update the local_recipi‐
3548 ent_maps setting if:
3549 • You redefine the local delivery agent in master.cf.
3551 • You redefine the "local_transport" setting in main.cf.
3553 • You use the "luser_relay", "mailbox_transport", or "fall‐
3555 back_transport" feature of the Postfix local(8) delivery agent.
3556 Details are described in the LOCAL_RECIPIENT_README file.
3558 Beware: if the Postfix SMTP server runs chrooted, you need to access
3560 the passwd file via the proxymap(8) service, in order to overcome ch‐
3561 root access restrictions. The alternative, maintaining a copy of the
3562 system password file in the chroot jail is not practical.
3563 Examples:
3565 local_recipient_maps =
3567
3569 The default mail delivery transport and next-hop destination for final
3570 delivery to domains listed with mydestination, and for [ipaddress] des‐
3571 tinations that match $inet_interfaces or $proxy_interfaces. This in‐
3572 formation can be overruled with the transport(5) table.
3573 By default, local mail is delivered to the transport called "local",
3575 which is just the name of a service that is defined the master.cf file.
3576 Specify a string of the form transport:nexthop, where transport is the
3578 name of a mail delivery transport defined in master.cf. The :nexthop
3579 destination is optional; its syntax is documented in the manual page of
3580 the corresponding delivery agent.
3581 Beware: if you override the default local delivery agent then you need
3583 to review the LOCAL_RECIPIENT_README document, otherwise the SMTP
3584 server may reject mail for local recipients.
3585
3587 Optional catch-all destination for unknown local(8) recipients. By de‐
3588 fault, mail for unknown recipients in domains that match $mydestina‐
3589 tion, $inet_interfaces or $proxy_interfaces is returned as undeliver‐
3590 able.
3591 The luser_relay value is not subject to Postfix configuration parameter
3593 $name expansion. Instead, the following $name expansions are done:
3594 $domain
3596 The recipient domain.
3597 $extension
3599 The recipient address extension.
3600 $home The recipient's home directory.
3602 $local The entire recipient address localpart.
3604 $recipient
3606 The full recipient address.
3607 $recipient_delimiter
3609 The address extension delimiter that was found in the recipient
3610 address (Postfix 2.11 and later), or the system-wide recipient
3611 address extension delimiter (Postfix 2.10 and earlier).
3612 $shell The recipient's login shell.
3614 $user The recipient username.
3616 ${name?value}
3618 Expands to value when $name has a non-empty value.
3619 ${name:value}
3621 Expands to value when $name has an empty value.
3622 Instead of $name you can also specify ${name} or $(name).
3624 Note: luser_relay works only for the Postfix local(8) delivery agent.
3626 Note: if you use this feature for accounts not in the UNIX password
3628 file, then you must specify "local_recipient_maps =" (i.e. empty) in
3629 the main.cf file, otherwise the Postfix SMTP server will reject mail
3630 for non-UNIX accounts with "User unknown in local recipient table".
3631 Examples:
3633 luser_relay = $user@other.host
3635 luser_relay = $local@other.host
3636 luser_relay = admin+$local
3637
3639 The mail system name that is displayed in Received: headers, in the
3640 SMTP greeting banner, and in bounced mail.
3641
3643 The UNIX system account that owns the Postfix queue and most Postfix
3644 daemon processes. Specify the name of an unprivileged user account
3645 that does not share a user or group ID with other accounts, and that
3646 owns no other files or processes on the system. In particular, don't
3647 specify nobody or daemon. PLEASE USE A DEDICATED USER ID AND GROUP ID.
3648 When this parameter value is changed you need to re-run "postfix
3650 set-permissions" (with Postfix version 2.0 and earlier: "/etc/post‐
3651 fix/post-install set-permissions".
3652
3654 The Postfix release date, in "YYYYMMDD" format.
3655
3657 The directory where local(8) UNIX-style mailboxes are kept. The default
3658 setting depends on the system type. Specify a name ending in / for
3659 maildir-style delivery.
3660 Note: maildir delivery is done with the privileges of the recipient.
3662 If you use the mail_spool_directory setting for maildir style delivery,
3663 then you must create the top-level maildir directory in advance. Post‐
3664 fix will not create it.
3665 Examples:
3667 mail_spool_directory = /var/mail
3669 mail_spool_directory = /var/spool/mail
3670
3672 The version of the mail system. Stable releases are named major.mi‐
3673 nor.patchlevel. Experimental releases also include the release date.
3674 The version string can be used in, for example, the SMTP greeting ban‐
3675 ner.
3676
3678 Optional external command that the local(8) delivery agent should use
3679 for mailbox delivery. The command is run with the user ID and the pri‐
3680 mary group ID privileges of the recipient. Exception: command delivery
3681 for root executes with $default_privs privileges. This is not a prob‐
3682 lem, because 1) mail for root should always be aliased to a real user
3683 and 2) don't log in as root, use "su" instead.
3684 The following environment variables are exported to the command:
3686 CLIENT_ADDRESS
3688 Remote client network address. Available in Postfix version 2.2
3689 and later.
3690 CLIENT_HELO
3692 Remote client EHLO command parameter. Available in Postfix ver‐
3693 sion 2.2 and later.
3694 CLIENT_HOSTNAME
3696 Remote client hostname. Available in Postfix version 2.2 and
3697 later.
3698 CLIENT_PROTOCOL
3700 Remote client protocol. Available in Postfix version 2.2 and
3701 later.
3702 DOMAIN The domain part of the recipient address.
3704 EXTENSION
3706 The optional address extension.
3707 HOME The recipient home directory.
3709 LOCAL The recipient address localpart.
3711 LOGNAME
3713 The recipient's username.
3714 ORIGINAL_RECIPIENT
3716 The entire recipient address, before any address rewriting or
3717 aliasing.
3718 RECIPIENT
3720 The full recipient address.
3721 SASL_METHOD
3723 SASL authentication method specified in the remote client AUTH
3724 command. Available in Postfix version 2.2 and later.
3725 SASL_SENDER
3727 SASL sender address specified in the remote client MAIL FROM
3728 command. Available in Postfix version 2.2 and later.
3729 SASL_USER
3731 SASL username specified in the remote client AUTH command.
3732 Available in Postfix version 2.2 and later.
3733 SENDER The full sender address.
3735 SHELL The recipient's login shell.
3737 USER The recipient username.
3739 Unlike other Postfix configuration parameters, the mailbox_command pa‐
3741 rameter is not subjected to $name substitutions. This is to make it
3742 easier to specify shell syntax (see example below).
3743 If you can, avoid shell meta characters because they will force Postfix
3745 to run an expensive shell process. If you're delivering via "procmail"
3746 then running a shell won't make a noticeable difference in the total
3747 cost.
3748 Note: if you use the mailbox_command feature to deliver mail sys‐
3750 tem-wide, you must set up an alias that forwards mail for root to a
3751 real user.
3752 The precedence of local(8) delivery features from high to low is:
3754 aliases, .forward files, mailbox_transport_maps, mailbox_transport,
3755 mailbox_command_maps, mailbox_command, home_mailbox, mail_spool_direc‐
3756 tory, fallback_transport_maps, fallback_transport and luser_relay.
3757 Examples:
3759 mailbox_command = /some/where/procmail
3761 mailbox_command = /some/where/procmail -a "$EXTENSION"
3762 mailbox_command = /some/where/maildrop -d "$USER"
3763 -f "$SENDER" "$EXTENSION"
3764
3766 Optional lookup tables with per-recipient external commands to use for
3767 local(8) mailbox delivery. Behavior is as with mailbox_command.
3768 The precedence of local(8) delivery features from high to low is:
3770 aliases, .forward files, mailbox_transport_maps, mailbox_transport,
3771 mailbox_command_maps, mailbox_command, home_mailbox, mail_spool_direc‐
3772 tory, fallback_transport_maps, fallback_transport and luser_relay.
3773 Specify zero or more "type:name" lookup tables, separated by whitespace
3775 or comma. Tables will be searched in the specified order until a match
3776 is found.
3777
3779 How to lock a UNIX-style local(8) mailbox before attempting delivery.
3780 For a list of available file locking methods, use the "postconf -l"
3781 command.
3782 This setting is ignored with maildir style delivery, because such de‐
3784 liveries are safe without explicit locks.
3785 Note: The dotlock method requires that the recipient UID or GID has
3787 write access to the parent directory of the mailbox file.
3788 Note: the default setting of this parameter is system dependent.
3790
3792 The maximal size of any local(8) individual mailbox or maildir file, or
3793 zero (no limit). In fact, this limits the size of any file that is
3794 written to upon local delivery, including files written by external
3795 commands that are executed by the local(8) delivery agent.
3796 This limit must not be smaller than the message size limit.
3798
3800 Optional message delivery transport that the local(8) delivery agent
3801 should use for mailbox delivery to all local recipients, whether or not
3802 they are found in the UNIX passwd database.
3803 The precedence of local(8) delivery features from high to low is:
3805 aliases, .forward files, mailbox_transport_maps, mailbox_transport,
3806 mailbox_command_maps, mailbox_command, home_mailbox, mail_spool_direc‐
3807 tory, fallback_transport_maps, fallback_transport and luser_relay.
3808
3810 Optional lookup tables with per-recipient message delivery transports
3811 to use for local(8) mailbox delivery, whether or not the recipients are
3812 found in the UNIX passwd database.
3813 The precedence of local(8) delivery features from high to low is:
3815 aliases, .forward files, mailbox_transport_maps, mailbox_transport,
3816 mailbox_command_maps, mailbox_command, home_mailbox, mail_spool_direc‐
3817 tory, fallback_transport_maps, fallback_transport and luser_relay.
3818 Specify zero or more "type:name" lookup tables, separated by whitespace
3820 or comma. Tables will be searched in the specified order until a match
3821 is found.
3822 For safety reasons, this feature does not allow $number substitutions
3824 in regular expression maps.
3825 This feature is available in Postfix 2.3 and later.
3827
3829 The name of an optional logfile that is written by the Postfix post‐
3830 logd(8) service. An empty value selects logging to syslogd(8). Specify
3831 "/dev/stdout" to select logging to standard output. Stdout logging re‐
3832 quires that Postfix is started with "postfix start-fg".
3833 Note 1: The maillog_file parameter value must contain a prefix that is
3835 specified with the maillog_file_prefixes parameter.
3836 Note 2: Some Postfix non-daemon programs may still log information to
3838 syslogd(8), before they have processed their configuration parameters
3839 and command-line options.
3840 This feature is available in Postfix 3.4 and later.
3842
3844 The program to run after rotating $maillog_file with "postfix logro‐
3845 tate". The command is run with the rotated logfile name as its first
3846 argument.
3847 This feature is available in Postfix 3.4 and later.
3849
3851 A list of allowed prefixes for a maillog_file value. This is a safety
3852 feature to contain the damage from a single configuration mistake.
3853 Specify one or more prefix strings, separated by comma or whitespace.
3854 This feature is available in Postfix 3.4 and later.
3856
3858 The format of the suffix to append to $maillog_file while rotating the
3859 file with "postfix logrotate". See strftime(3) for syntax. The default
3860 suffix, YYYYMMDD-HHMMSS, allows logs to be rotated frequently.
3861 This feature is available in Postfix 3.4 and later.
3863
3865 Sendmail compatibility feature that specifies where the Postfix
3866 mailq(1) command is installed. This command can be used to list the
3867 Postfix mail queue.
3868
3870 Where the Postfix manual pages are installed.
3871
3873 Obsolete feature: use the reject_rbl_client feature instead.
3874
3876 The numerical Postfix SMTP server response code when a remote SMTP
3877 client request is blocked by the reject_rbl_client, re‐
3878 ject_rhsbl_client, reject_rhsbl_reverse_client, reject_rhsbl_sender or
3879 reject_rhsbl_recipient restriction.
3880 Do not change this unless you have a complete understanding of RFC
3882 5321.
3883
3885 What addresses are subject to address masquerading.
3887 By default, address masquerading is limited to envelope sender ad‐
3889 dresses, and to header sender and header recipient addresses. This al‐
3890 lows you to use address masquerading on a mail gateway while still be‐
3891 ing able to forward mail to users on individual machines.
3892 Specify zero or more of: envelope_sender, envelope_recipient,
3894 header_sender, header_recipient
3895
3897 Optional list of domains whose subdomain structure will be stripped off
3898 in email addresses.
3899 The list is processed left to right, and processing stops at the first
3901 match. Thus,
3902 masquerade_domains = foo.example.com example.com
3904 strips "user@any.thing.foo.example.com" to "user@foo.example.com", but
3906 strips "user@any.thing.else.example.com" to "user@example.com".
3907 A domain name prefixed with ! means do not masquerade this domain or
3909 its subdomains. Thus,
3910 masquerade_domains = !foo.example.com example.com
3912 does not change "user@any.thing.foo.example.com" or "user@foo.exam‐
3914 ple.com", but strips "user@any.thing.else.example.com" to "user@exam‐
3915 ple.com".
3916 Note: with Postfix version 2.2, message header address masquerading
3918 happens only when message header address rewriting is enabled:
3919 • The message is received with the Postfix sendmail(1) command,
3921 • The message is received from a network client that matches $lo‐
3923 cal_header_rewrite_clients,
3924 • The message is received from the network, and the re‐
3926 mote_header_rewrite_domain parameter specifies a non-empty
3927 value.
3928 To get the behavior before Postfix version 2.2, specify "lo‐
3930 cal_header_rewrite_clients = static:all".
3931 Example:
3933 masquerade_domains = $mydomain
3935
3937 Optional list of user names that are not subjected to address mas‐
3938 querading, even when their addresses match $masquerade_domains.
3939 By default, address masquerading makes no exceptions.
3941 Specify a list of user names, "/file/name" or "type:table" patterns,
3943 separated by commas and/or whitespace. The list is matched left to
3944 right, and the search stops on the first match. A "/file/name" pattern
3945 is replaced by its contents; a "type:table" lookup table is matched
3946 when a name matches a lookup key (the lookup result is ignored). Con‐
3947 tinue long lines by starting the next line with whitespace. Specify
3948 "!pattern" to exclude a name from the list. The form "!/file/name" is
3949 supported only in Postfix version 2.4 and later.
3950 Examples:
3952 masquerade_exceptions = root, mailer-daemon
3954 masquerade_exceptions = root
3955
3957 Selectively disable master(8) listener ports by service type or by ser‐
3958 vice name and type. Specify a list of service types ("inet", "unix",
3959 "fifo", or "pass") or "name/type" tuples, where "name" is the first
3960 field of a master.cf entry and "type" is a service type. As with other
3961 Postfix matchlists, a search stops at the first match. Specify "!pat‐
3962 tern" to exclude a service from the list. By default, all master(8)
3963 listener ports are enabled.
3964 Note: this feature does not support "/file/name" or "type:table" pat‐
3966 terns, nor does it support wildcards such as "*" or "all". This is in‐
3967 tentional.
3968 Examples:
3970 # With Postfix 2.6..2.10 use '.' instead of '/'.
3972 # Turn on all master(8) listener ports (the default).
3973 master_service_disable =
3974 # Turn off only the main SMTP listener port.
3975 master_service_disable = smtp/inet
3976 # Turn off all TCP/IP listener ports.
3977 master_service_disable = inet
3978 # Turn off all TCP/IP listener ports except "foo".
3979 master_service_disable = !foo/inet, inet
3980 This feature is available in Postfix 2.6 and later.
3982
3984 The maximum amount of time that an idle Postfix daemon process waits
3985 for an incoming connection before terminating voluntarily. This param‐
3986 eter is ignored by the Postfix queue manager and by other long-lived
3987 Postfix daemon processes.
3988 Time units: s (seconds), m (minutes), h (hours), d (days), w (weeks).
3990 The default time unit is s (seconds).
3991
3993 The maximal number of incoming connections that a Postfix daemon
3994 process will service before terminating voluntarily. This parameter is
3995 ignored by the Postfix queue manager and by other long-lived Postfix
3996 daemon processes.
3997
3999 The maximal time between attempts to deliver a deferred message.
4000 This parameter should be set to a value greater than or equal to $mini‐
4002 mal_backoff_time. See also $queue_run_delay.
4003 Time units: s (seconds), m (minutes), h (hours), d (days), w (weeks).
4005 The default time unit is s (seconds).
4006
4008 Consider a message as undeliverable, when delivery fails with a tempo‐
4009 rary error, and the time in the queue has reached the maxi‐
4010 mal_queue_lifetime limit.
4011 Time units: s (seconds), m (minutes), h (hours), d (days), w (weeks).
4013 The default time unit is d (days).
4014 Specify 0 when mail delivery should be tried only once.
4016
4018 Names of message headers that the cleanup(8) daemon will remove after
4019 applying header_checks(5) and before invoking Milter applications. The
4020 default setting is compatible with Postfix < 3.0.
4021 Specify a list of header names, separated by comma or space. Names are
4023 matched in a case-insensitive manner. The list of supported header
4024 names is limited only by available memory.
4025 This feature is available in Postfix 3.0 and later.
4027
4029 The set of characters that Postfix will reject in message content. The
4030 usual C-like escape sequences are recognized: \a \b \f \n \r \t \v \ddd
4031 (up to three octal digits) and \\.
4032 Note 1: this feature does not recognize text that requires MIME decod‐
4034 ing. It inspects raw message content, just like header_checks and
4035 body_checks.
4036 Note 2: this feature is disabled with "receive_override_options =
4038 no_header_body_checks".
4039 Example:
4041 message_reject_characters = \0
4043 This feature is available in Postfix 2.3 and later.
4045
4047 The maximal size in bytes of a message, including envelope information.
4048 Note: be careful when making changes. Excessively small values will
4050 result in the loss of non-delivery notifications, when a bounce message
4051 size exceeds the local or remote MTA's message size limit.
4052
4054 The set of characters that Postfix will remove from message content.
4055 The usual C-like escape sequences are recognized: \a \b \f \n \r \t \v
4056 \ddd (up to three octal digits) and \\.
4057 Note 1: this feature does not recognize text that requires MIME decod‐
4059 ing. It inspects raw message content, just like header_checks and
4060 body_checks.
4061 Note 2: this feature is disabled with "receive_override_options =
4063 no_header_body_checks".
4064 Example:
4066 message_strip_characters = \0
4068 This feature is available in Postfix 2.3 and later.
4070
4072 The location of non-executable files that are shared among multiple
4073 Postfix instances, such as postfix-files, dynamicmaps.cf, and the
4074 multi-instance template files main.cf.proto and master.cf.proto. This
4075 directory should contain only Postfix-related files. Typically, the
4076 meta_directory parameter has the same default as the config_directory
4077 parameter (/etc/postfix or /usr/local/etc/postfix).
4078 For backwards compatibility with Postfix versions 2.6..2.11, specify
4080 "meta_directory = $daemon_directory" in main.cf before installing or
4081 upgrading Postfix, or specify "meta_directory = /path/name" on the
4082 "make makefiles", "make install" or "make upgrade" command line.
4083 This feature is available in Postfix 3.0 and later.
4085
4087 The time limit for sending an SMTP command to a Milter (mail filter)
4088 application, and for receiving the response.
4089 Specify a non-zero time value (an integral value plus an optional
4091 one-letter suffix that specifies the time unit).
4092 Time units: s (seconds), m (minutes), h (hours), d (days), w (weeks).
4094 The default time unit is s (seconds).
4095 This feature is available in Postfix 2.3 and later.
4097
4099 The macros that are sent to Milter (mail filter) applications after
4100 completion of an SMTP connection. See MILTER_README for a list of
4101 available macro names and their meanings.
4102 This feature is available in Postfix 2.3 and later.
4104
4106 The time limit for connecting to a Milter (mail filter) application,
4107 and for negotiating protocol options.
4108 Specify a non-zero time value (an integral value plus an optional
4110 one-letter suffix that specifies the time unit).
4111 Time units: s (seconds), m (minutes), h (hours), d (days), w (weeks).
4113 The default time unit is s (seconds).
4114 This feature is available in Postfix 2.3 and later.
4116
4118 The time limit for sending message content to a Milter (mail filter)
4119 application, and for receiving the response.
4120 Specify a non-zero time value (an integral value plus an optional
4122 one-letter suffix that specifies the time unit).
4123 Time units: s (seconds), m (minutes), h (hours), d (days), w (weeks).
4125 The default time unit is s (seconds).
4126 This feature is available in Postfix 2.3 and later.
4128
4130 The macros that are sent to version 4 or higher Milter (mail filter)
4131 applications after the SMTP DATA command. See MILTER_README for a list
4132 of available macro names and their meanings.
4133 This feature is available in Postfix 2.3 and later.
4135
4137 The default action when a Milter (mail filter) response is unavailable
4138 (for example, bad Postfix configuration or Milter failure). Specify one
4139 of the following:
4140 accept Proceed as if the mail filter was not present.
4142 reject Reject all further commands in this session with a permanent
4144 status code.
4145 tempfail
4147 Reject all further commands in this session with a temporary
4148 status code.
4149 quarantine
4151 Like "accept", but freeze the message in the "hold" queue.
4152 Available with Postfix 2.6 and later.
4153 This feature is available in Postfix 2.3 and later.
4155
4157 The macros that are sent to Milter (mail filter) applications after the
4158 message end-of-data. See MILTER_README for a list of available macro
4159 names and their meanings.
4160 This feature is available in Postfix 2.3 and later.
4162
4164 The macros that are sent to Milter (mail filter) applications after the
4165 end of the message header. See MILTER_README for a list of available
4166 macro names and their meanings.
4167 This feature is available in Postfix 2.5 and later.
4169
4171 Optional lookup tables for content inspection of message headers that
4172 are produced by Milter applications. See the header_checks(5) manual
4173 page available actions. Currently, PREPEND is not implemented.
4174 The following example sends all mail that is marked as SPAM to a spam
4176 handling machine. Note that matches are case-insensitive by default.
4177 /etc/postfix/main.cf:
4179 milter_header_checks = pcre:/etc/postfix/milter_header_checks
4180 /etc/postfix/milter_header_checks:
4182 /^X-SPAM-FLAG:\s+YES/ FILTER mysmtp:sanitizer.example.com:25
4183 The milter_header_checks mechanism could also be used for allowlisting.
4185 For example it could be used to skip heavy content inspection for
4186 DKIM-signed mail from known friendly domains.
4187 This feature is available in Postfix 2.7, and as an optional patch for
4189 Postfix 2.6.
4190
4192 The macros that are sent to Milter (mail filter) applications after the
4193 SMTP HELO or EHLO command. See MILTER_README for a list of available
4194 macro names and their meanings.
4195 This feature is available in Postfix 2.3 and later.
4197
4199 The {daemon_name} macro value for Milter (mail filter) applications.
4200 See MILTER_README for a list of available macro names and their mean‐
4201 ings.
4202 This feature is available in Postfix 2.3 and later.
4204
4206 Optional list of name=value pairs that specify default values for arbi‐
4207 trary macros that Postfix may send to Milter applications. These de‐
4208 faults are used when there is no corresponding information from the
4209 message delivery context.
4210 Specify name=value or {name}=value pairs separated by comma or white‐
4212 space. Enclose a pair in "{}" when a value contains comma or white‐
4213 space (this form ignores whitespace after the enclosing "{", around the
4214 "=", and before the enclosing "}").
4215 This feature is available in Postfix 3.1 and later.
4217
4219 The {v} macro value for Milter (mail filter) applications. See MIL‐
4220 TER_README for a list of available macro names and their meanings.
4221 This feature is available in Postfix 2.3 and later.
4223
4225 The macros that are sent to Milter (mail filter) applications after the
4226 SMTP MAIL FROM command. See MILTER_README for a list of available macro
4227 names and their meanings.
4228 This feature is available in Postfix 2.3 and later.
4230
4232 The mail filter protocol version and optional protocol extensions for
4233 communication with a Milter application; prior to Postfix 2.6 the de‐
4234 fault protocol is 2. Postfix sends this version number during the ini‐
4235 tial protocol handshake. It should match the version number that is
4236 expected by the mail filter application (or by its Milter library).
4237 Protocol versions:
4239 2 Use Sendmail 8 mail filter protocol version 2 (default with
4241 Sendmail version 8.11 .. 8.13 and Postfix version 2.3 .. 2.5).
4242 3 Use Sendmail 8 mail filter protocol version 3.
4244 4 Use Sendmail 8 mail filter protocol version 4.
4246 6 Use Sendmail 8 mail filter protocol version 6 (default with
4248 Sendmail version 8.14 and Postfix version 2.6).
4249 Protocol extensions:
4251 no_header_reply
4253 Specify this when the Milter application will not reply for each
4254 individual message header.
4255 This feature is available in Postfix 2.3 and later.
4257
4259 The macros that are sent to Milter (mail filter) applications after the
4260 SMTP RCPT TO command. See MILTER_README for a list of available macro
4261 names and their meanings.
4262 This feature is available in Postfix 2.3 and later.
4264
4266 The macros that are sent to version 3 or higher Milter (mail filter)
4267 applications after an unknown SMTP command. See MILTER_README for a
4268 list of available macro names and their meanings.
4269 This feature is available in Postfix 2.3 and later.
4271
4273 The maximal length of MIME multipart boundary strings. The MIME proces‐
4274 sor is unable to distinguish between boundary strings that do not dif‐
4275 fer in the first $mime_boundary_length_limit characters.
4276 This feature is available in Postfix 2.0 and later.
4278
4280 Optional lookup tables for content inspection of MIME related message
4281 headers, as described in the header_checks(5) manual page.
4282 This feature is available in Postfix 2.0 and later.
4284
4286 The maximal recursion level that the MIME processor will handle. Post‐
4287 fix refuses mail that is nested deeper than the specified limit.
4288 This feature is available in Postfix 2.0 and later.
4290
4292 The minimal time between attempts to deliver a deferred message; prior
4293 to Postfix 2.4 the default value was 1000s.
4294 This parameter also limits the time an unreachable destination is kept
4296 in the short-term, in-memory, destination status cache.
4297 This parameter should be set greater than or equal to $queue_run_delay.
4299 See also $maximal_backoff_time.
4300 Time units: s (seconds), m (minutes), h (hours), d (days), w (weeks).
4302 The default time unit is s (seconds).
4303
4305 An optional list of non-default Postfix configuration directories;
4306 these directories belong to additional Postfix instances that share the
4307 Postfix executable files and documentation with the default Postfix in‐
4308 stance, and that are started, stopped, etc., together with the default
4309 Postfix instance. Specify a list of pathnames separated by comma or
4310 whitespace.
4311 When $multi_instance_directories is empty, the postfix(1) command runs
4313 in single-instance mode and operates on a single Postfix instance only.
4314 Otherwise, the postfix(1) command runs in multi-instance mode and in‐
4315 vokes the multi-instance manager specified with the multi_in‐
4316 stance_wrapper parameter. The multi-instance manager in turn executes
4317 postfix(1) commands for the default instance and for all Postfix in‐
4318 stances in $multi_instance_directories.
4319 Currently, this parameter setting is ignored except for the default
4321 main.cf file.
4322 This feature is available in Postfix 2.6 and later.
4324
4326 Allow this Postfix instance to be started, stopped, etc., by a
4327 multi-instance manager. By default, new instances are created in a
4328 safe state that prevents them from being started inadvertently. This
4329 parameter is reserved for the multi-instance manager.
4330 This feature is available in Postfix 2.6 and later.
4332
4334 The optional instance group name of this Postfix instance. A group
4335 identifies closely-related Postfix instances that the multi-instance
4336 manager can start, stop, etc., as a unit. This parameter is reserved
4337 for the multi-instance manager.
4338 This feature is available in Postfix 2.6 and later.
4340
4342 The optional instance name of this Postfix instance. This name becomes
4343 also the default value for the syslog_name parameter.
4344 This feature is available in Postfix 2.6 and later.
4346
4348 The pathname of a multi-instance manager command that the postfix(1)
4349 command invokes when the multi_instance_directories parameter value is
4350 non-empty. The pathname may be followed by initial command arguments
4351 separated by whitespace; shell metacharacters such as quotes are not
4352 supported in this context.
4353 The postfix(1) command invokes the manager command with the postfix(1)
4355 non-option command arguments on the manager command line, and with all
4356 installation configuration parameters exported into the manager command
4357 process environment. The manager command in turn invokes the postfix(1)
4358 command for individual Postfix instances as "postfix -c config_direc‐
4359 tory command".
4360 This feature is available in Postfix 2.6 and later.
4362
4364 The numerical Postfix SMTP server response code when a remote SMTP
4365 client request is blocked by the reject_multi_recipient_bounce restric‐
4366 tion.
4367 Do not change this unless you have a complete understanding of RFC
4369 5321.
4370 This feature is available in Postfix 2.1 and later.
4372
4374 The list of domains that are delivered via the $local_transport mail
4375 delivery transport. By default this is the Postfix local(8) delivery
4376 agent which looks up all recipients in /etc/passwd and /etc/aliases.
4377 The SMTP server validates recipient addresses with $local_recipi‐
4378 ent_maps and rejects non-existent recipients. See also the local domain
4379 class in the ADDRESS_CLASS_README file.
4380 The default mydestination value specifies names for the local machine
4382 only. On a mail domain gateway, you should also include $mydomain.
4383 The $local_transport delivery method is also selected for mail ad‐
4385 dressed to user@[the.net.work.address] of the mail system (the IP ad‐
4386 dresses specified with the inet_interfaces and proxy_interfaces parame‐
4387 ters).
4388 Warnings:
4390 • Do not specify the names of virtual domains - those domains are
4392 specified elsewhere. See VIRTUAL_README for more information.
4393 • Do not specify the names of domains that this machine is backup
4395 MX host for. See STANDARD_CONFIGURATION_README for how to set up
4396 backup MX hosts.
4397 • By default, the Postfix SMTP server rejects mail for recipients
4399 not listed with the local_recipient_maps parameter. See the
4400 postconf(5) manual for a description of the local_recipient_maps
4401 and unknown_local_recipient_reject_code parameters.
4402 Specify a list of host or domain names, "/file/name" or "type:table"
4404 patterns, separated by commas and/or whitespace. A "/file/name" pattern
4405 is replaced by its contents; a "type:table" lookup table is matched
4406 when a name matches a lookup key (the lookup result is ignored). Con‐
4407 tinue long lines by starting the next line with whitespace.
4408 Examples:
4410 mydestination = $myhostname, localhost.$mydomain $mydomain
4412 mydestination = $myhostname, localhost.$mydomain www.$mydomain, ftp.$mydomain
4413
4415 The internet domain name of this mail system. The default is to use
4416 $myhostname minus the first component, or "localdomain" (Postfix 2.3
4417 and later). $mydomain is used as a default value for many other con‐
4418 figuration parameters.
4419 Example:
4421 mydomain = domain.tld
4423
4425 The internet hostname of this mail system. The default is to use the
4426 fully-qualified domain name (FQDN) from gethostname(), or to use the
4427 non-FQDN result from gethostname() and append ".$mydomain". $myhost‐
4428 name is used as a default value for many other configuration parame‐
4429 ters.
4430 Example:
4432 myhostname = host.example.com
4434
4436 The list of "trusted" remote SMTP clients that have more privileges
4437 than "strangers".
4438 In particular, "trusted" SMTP clients are allowed to relay mail through
4440 Postfix. See the smtpd_relay_restrictions parameter description in the
4441 postconf(5) manual.
4442 You can specify the list of "trusted" network addresses by hand or you
4444 can let Postfix do it for you (which is the default). See the descrip‐
4445 tion of the mynetworks_style parameter for more information.
4446 If you specify the mynetworks list by hand, Postfix ignores the mynet‐
4448 works_style setting.
4449 Specify a list of network addresses or network/netmask patterns, sepa‐
4451 rated by commas and/or whitespace. Continue long lines by starting the
4452 next line with whitespace.
4453 The netmask specifies the number of bits in the network part of a host
4455 address. You can also specify "/file/name" or "type:table" patterns.
4456 A "/file/name" pattern is replaced by its contents; a "type:table"
4457 lookup table is matched when a table entry matches a lookup string (the
4458 lookup result is ignored).
4459 The list is matched left to right, and the search stops on the first
4461 match. Specify "!pattern" to exclude an address or network block from
4462 the list. The form "!/file/name" is supported only in Postfix version
4463 2.4 and later.
4464 Note 1: Pattern matching of domain names is controlled by the or ab‐
4466 sence of "mynetworks" in the parent_domain_matches_subdomains parameter
4467 value.
4468 Note 2: IP version 6 address information must be specified inside [] in
4470 the mynetworks value, and in files specified with "/file/name". IP
4471 version 6 addresses contain the ":" character, and would otherwise be
4472 confused with a "type:table" pattern.
4473 Examples:
4475 mynetworks = 127.0.0.0/8 168.100.189.0/28
4477 mynetworks = !192.168.0.1, 192.168.0.0/28
4478 mynetworks = 127.0.0.0/8 168.100.189.0/28 [::1]/128 [2001:240:587::]/64
4479 mynetworks = $config_directory/mynetworks
4480 mynetworks = hash:/etc/postfix/network_table
4481
4483 The method to generate the default value for the mynetworks parameter.
4484 This is the list of trusted networks for relay access control etc.
4485 • Specify "mynetworks_style = host" when Postfix should "trust"
4487 only the local machine.
4488 • Specify "mynetworks_style = subnet" when Postfix should "trust"
4490 remote SMTP clients in the same IP subnetworks as the local ma‐
4491 chine. On Linux, this works correctly only with interfaces
4492 specified with the "ifconfig" command.
4493 • Specify "mynetworks_style = class" when Postfix should "trust"
4495 remote SMTP clients in the same IP class A/B/C networks as the
4496 local machine. Caution: this may cause Postfix to "trust" your
4497 entire provider's network. Instead, specify an explicit mynet‐
4498 works list by hand, as described with the mynetworks configura‐
4499 tion parameter.
4500
4502 The domain name that locally-posted mail appears to come from, and that
4503 locally posted mail is delivered to. The default, $myhostname, is ade‐
4504 quate for small sites. If you run a domain with multiple machines, you
4505 should (1) change this to $mydomain and (2) set up a domain-wide alias
4506 database that aliases each user to user@that.users.mailhost.
4507 Example:
4509 myorigin = $mydomain
4511
4513 Optional lookup tables for content inspection of non-MIME message head‐
4514 ers in attached messages, as described in the header_checks(5) manual
4515 page.
4516 This feature is available in Postfix 2.0 and later.
4518
4520 Sendmail compatibility feature that specifies the location of the
4521 newaliases(1) command. This command can be used to rebuild the local(8)
4522 aliases(5) database.
4523
4525 The numerical Postfix SMTP server reply code when a client request is
4526 rejected by the reject_non_fqdn_helo_hostname, reject_non_fqdn_sender
4527 or reject_non_fqdn_recipient restriction.
4528
4530 A list of Milter (mail filter) applications for new mail that does not
4531 arrive via the Postfix smtpd(8) server. This includes local submission
4532 via the sendmail(1) command line, new mail that arrives via the Postfix
4533 qmqpd(8) server, and old mail that is re-injected into the queue with
4534 "postsuper -r". Specify space or comma as separator. See the MIL‐
4535 TER_README document for details.
4536 This feature is available in Postfix 2.3 and later.
4538
4540 The list of error classes that are reported to the postmaster. The de‐
4541 fault is to report only the most serious problems. The paranoid may
4542 wish to turn on the policy (UCE and mail relaying) and protocol error
4543 (broken mail software) reports.
4544 NOTE: postmaster notifications may contain confidential information
4546 such as SASL passwords or message content. It is the system adminis‐
4547 trator's responsibility to treat such information with care.
4548 The error classes are:
4550 bounce (also implies 2bounce)
4552 Send the postmaster copies of the headers of bounced mail, and
4553 send transcripts of SMTP sessions when Postfix rejects mail. The
4554 notification is sent to the address specified with the
4555 bounce_notice_recipient configuration parameter (default: post‐
4556 master).
4557 2bounce
4559 Send undeliverable bounced mail to the postmaster. The notifica‐
4560 tion is sent to the address specified with the 2bounce_no‐
4561 tice_recipient configuration parameter (default: postmaster).
4562 data Send the postmaster a transcript of the SMTP session with an er‐
4564 ror because a critical data file was unavailable. The notifica‐
4565 tion is sent to the address specified with the error_notice_re‐
4566 cipient configuration parameter (default: postmaster).
4567 This feature is available in Postfix 2.9 and later.
4568 delay Send the postmaster copies of the headers of delayed mail (see
4570 delay_warning_time). The notification is sent to the address
4571 specified with the delay_notice_recipient configuration parame‐
4572 ter (default: postmaster).
4573 policy Send the postmaster a transcript of the SMTP session when a
4575 client request was rejected because of (UCE) policy. The notifi‐
4576 cation is sent to the address specified with the error_no‐
4577 tice_recipient configuration parameter (default: postmaster).
4578 protocol
4580 Send the postmaster a transcript of the SMTP session in case of
4581 client or server protocol errors. The notification is sent to
4582 the address specified with the error_notice_recipient configura‐
4583 tion parameter (default: postmaster).
4584 resource
4586 Inform the postmaster of mail not delivered due to resource
4587 problems. The notification is sent to the address specified
4588 with the error_notice_recipient configuration parameter (de‐
4589 fault: postmaster).
4590 software
4592 Inform the postmaster of mail not delivered due to software
4593 problems. The notification is sent to the address specified
4594 with the error_notice_recipient configuration parameter (de‐
4595 fault: postmaster).
4596 Examples:
4598 notify_classes = bounce, delay, policy, protocol, resource, software
4600 notify_classes = 2bounce, resource, software
4601
4603 The numerical reply code when the Postfix SMTP server rejects a sender
4604 or recipient address because its domain has a nullmx DNS record (an MX
4605 record with an empty hostname). This is one of the possible replies
4606 from the restrictions reject_unknown_sender_domain and reject_un‐
4607 known_recipient_domain.
4608 This feature is available in Postfix 3.0 and later.
4610
4612 The location of the OpenSSL command line program openssl(1). This is
4613 used by the "postfix tls" command to create private keys, certificate
4614 signing requests, self-signed certificates, and to compute public key
4615 digests for DANE TLSA records. In multi-instance environments, this
4616 parameter is always determined from the configuration of the default
4617 Postfix instance.
4618 Example:
4620 /etc/postfix/main.cf:
4622 # NetBSD pkgsrc:
4623 openssl_path = /usr/pkg/bin/openssl
4624 # Local build:
4625 openssl_path = /usr/local/bin/openssl
4626 This feature is available in Postfix 3.1 and later.
4628
4630 Enable special treatment for owner-listname entries in the aliases(5)
4631 file, and don't split owner-listname and listname-request address lo‐
4632 calparts when the recipient_delimiter is set to "-". This feature is
4633 useful for mailing lists.
4634
4636 A list of Postfix features where the pattern "example.com" also matches
4637 subdomains of example.com, instead of requiring an explicit ".exam‐
4638 ple.com" pattern. This is planned backwards compatibility: eventu‐
4639 ally, all Postfix features are expected to require explicit ".exam‐
4640 ple.com" style patterns when you really want to match subdomains.
4641 The following Postfix feature names are supported.
4643 Postfix version 1.0 and later
4645 debug_peer_list, fast_flush_domains, mynetworks, per‐
4646 mit_mx_backup_networks, relay_domains, transport_maps
4647 Postfix version 1.1 and later
4649 qmqpd_authorized_clients, smtpd_access_maps,
4650 Postfix version 2.8 and later
4652 postscreen_access_list
4653 Postfix version 3.0 and later
4655 smtpd_client_event_limit_exceptions
4656
4658 Restrict the use of the permit_mx_backup SMTP access feature to only
4659 domains whose primary MX hosts match the listed networks. The parame‐
4660 ter value syntax is the same as with the mynetworks parameter; note,
4661 however, that the default value is empty.
4662 Pattern matching of domain names is controlled by the presence or ab‐
4664 sence of "permit_mx_backup_networks" in the parent_domain_matches_sub‐
4665 domains parameter value.
4666
4668 The name of the pickup(8) service. This service picks up local mail
4669 submissions from the Postfix maildrop queue.
4670 This feature is available in Postfix 2.0 and later.
4672
4674 Optional filter for the pipe(8) delivery agent to change the delivery
4675 status code or explanatory text of successful or unsuccessful deliver‐
4676 ies. See default_delivery_status_filter for details.
4677 This feature is available in Postfix 3.0 and later.
4679
4681 The numerical Postfix SMTP server response code when a request is re‐
4682 jected by the reject_plaintext_session restriction.
4683 This feature is available in Postfix 2.3 and later.
4685
4687 The name of the postlogd(8) service entry in master.cf. This service
4688 appends logfile records to the file specified with the maillog_file pa‐
4689 rameter.
4690 This feature is available in Postfix 3.4 and later.
4692
4694 How much time a postlogd(8) process may take to process a request be‐
4695 fore it is terminated by a built-in watchdog timer. This is a safety
4696 mechanism that prevents postlogd(8) from becoming non-responsive due to
4697 a bug in Postfix itself or in system software. This limit cannot be set
4698 under 10s.
4699 Specify a non-zero time value (an integral value plus an optional
4701 one-letter suffix that specifies the time unit). Time units: s (sec‐
4702 onds), m (minutes), h (hours), d (days), w (weeks).
4703 This feature is available in Postfix 3.4 and later.
4705
4707 The postfix(1) commands that the postmulti(1) instance manager treats
4708 as "control" commands, that operate on running instances. For these
4709 commands, disabled instances are skipped.
4710 This feature is available in Postfix 2.6 and later.
4712
4714 The postfix(1) commands that the postmulti(1) instance manager treats
4715 as "start" commands. For these commands, disabled instances are
4716 "checked" rather than "started", and failure to "start" a member in‐
4717 stance of an instance group will abort the start-up of later instances.
4718 This feature is available in Postfix 2.6 and later.
4720
4722 The postfix(1) commands that the postmulti(1) instance manager treats
4723 as "stop" commands. For these commands, disabled instances are skipped,
4724 and enabled instances are processed in reverse order.
4725 This feature is available in Postfix 2.6 and later.
4727
4729 Permanent allow/denylist for remote SMTP client IP addresses.
4730 postscreen(8) searches this list immediately after a remote SMTP client
4731 connects. Specify a comma- or whitespace-separated list of commands
4732 (in upper or lower case) or lookup tables. The search stops upon the
4733 first command that fires for the client IP address.
4734 permit_mynetworks
4736 Allowlist the client and terminate the search if the client IP
4737 address matches $mynetworks. Do not subject the client to any
4738 before/after 220 greeting tests. Pass the connection immedi‐
4739 ately to a Postfix SMTP server process.
4740 Pattern matching of domain names is controlled by the presence
4741 or absence of "postscreen_access_list" in the parent_do‐
4742 main_matches_subdomains parameter value.
4743 type:table
4745 Query the specified lookup table. Each table lookup result is an
4746 access list, except that access lists inside a table cannot
4747 specify type:table entries.
4748 To discourage the use of hash, btree, etc. tables, there is no
4749 support for substring matching like smtpd(8). Use CIDR tables
4750 instead.
4751 permit
4753 Allowlist the client and terminate the search. Do not subject
4754 the client to any before/after 220 greeting tests. Pass the con‐
4755 nection immediately to a Postfix SMTP server process.
4756 reject
4758 Denylist the client and terminate the search. Subject the client
4759 to the action configured with the postscreen_denylist_action
4760 configuration parameter.
4761 dunno All postscreen(8) access lists implicitly have this command at
4763 the end.
4764 When dunno is executed inside a lookup table, return from the
4765 lookup table and evaluate the next command.
4766 When dunno is executed outside a lookup table, terminate the
4767 search, and subject the client to the configured before/after
4768 220 greeting tests.
4769 Example:
4771 /etc/postfix/main.cf:
4773 postscreen_access_list = permit_mynetworks,
4774 cidr:/etc/postfix/postscreen_access.cidr
4775 # Postfix < 3.6 use postscreen_blacklist_action.
4776 postscreen_denylist_action = enforce
4777 /etc/postfix/postscreen_access.cidr:
4779 # Rules are evaluated in the order as specified.
4780 # Denylist 192.168.* except 192.168.0.1.
4781 192.168.0.1 dunno
4782 192.168.0.0/16 reject
4783 This feature is available in Postfix 2.8.
4785
4787 A list of local postscreen(8) server IP addresses where a non-al‐
4788 lowlisted remote SMTP client can obtain postscreen(8)'s temporary al‐
4789 lowlist status. This status is required before the client can talk to a
4790 Postfix SMTP server process. By default, a client can obtain
4791 postscreen(8)'s allowlist status on any local postscreen(8) server IP
4792 address.
4793 When postscreen(8) listens on both primary and backup MX addresses, the
4795 postscreen_allowlist_interfaces parameter can be configured to give the
4796 temporary allowlist status only when a client connects to a primary MX
4797 address. Once a client is allowlisted it can talk to a Postfix SMTP
4798 server on any address. Thus, clients that connect only to backup MX ad‐
4799 dresses will never become allowlisted, and will never be allowed to
4800 talk to a Postfix SMTP server process.
4801 Specify a list of network addresses or network/netmask patterns, sepa‐
4803 rated by commas and/or whitespace. The netmask specifies the number of
4804 bits in the network part of a host address. Continue long lines by
4805 starting the next line with whitespace.
4806 You can also specify "/file/name" or "type:table" patterns. A
4808 "/file/name" pattern is replaced by its contents; a "type:table" lookup
4809 table is matched when a table entry matches a lookup string (the lookup
4810 result is ignored).
4811 The list is matched left to right, and the search stops on the first
4813 match. Specify "!pattern" to exclude an address or network block from
4814 the list.
4815 Note: IP version 6 address information must be specified inside [] in
4817 the postscreen_allowlist_interfaces value, and in files specified with
4818 "/file/name". IP version 6 addresses contain the ":" character, and
4819 would otherwise be confused with a "type:table" pattern.
4820 Example:
4822 /etc/postfix/main.cf:
4824 # Don't allowlist connections to the backup IP address.
4825 # Postfix < 3.6 use postscreen_whitelist_interfaces.
4826 postscreen_allowlist_interfaces = !168.100.189.8, static:all
4827 This feature is available in Postfix 3.6 and later.
4829 Available as postscreen_whitelist_interfaces in Postfix 2.9 - 3.5.
4831
4833 The action that postscreen(8) takes when a remote SMTP client sends a
4834 bare newline character, that is, a newline not preceded by carriage re‐
4835 turn. Specify one of the following:
4836 ignore Ignore the failure of this test. Allow other tests to complete.
4838 Do not repeat this test before some the result from some other
4839 test expires. This option is useful for testing and collecting
4840 statistics without blocking mail permanently.
4841 enforce
4843 Allow other tests to complete. Reject attempts to deliver mail
4844 with a 550 SMTP reply, and log the helo/sender/recipient infor‐
4845 mation. Repeat this test the next time the client connects.
4846 drop Drop the connection immediately with a 521 SMTP reply. Repeat
4848 this test the next time the client connects.
4849 This feature is available in Postfix 2.8.
4851
4853 Enable "bare newline" SMTP protocol tests in the postscreen(8) server.
4854 These tests are expensive: a remote SMTP client must disconnect after
4855 it passes the test, before it can talk to a real Postfix SMTP server.
4856 This feature is available in Postfix 2.8.
4858
4860 The amount of time that postscreen(8) will use the result from a suc‐
4861 cessful "bare newline" SMTP protocol test. During this time, the client
4862 IP address is excluded from this test. The default is long because a
4863 remote SMTP client must disconnect after it passes the test, before it
4864 can talk to a real Postfix SMTP server.
4865 Specify a non-zero time value (an integral value plus an optional
4867 one-letter suffix that specifies the time unit). Time units: s (sec‐
4868 onds), m (minutes), h (hours), d (days), w (weeks).
4869 This feature is available in Postfix 2.8.
4871
4873 Renamed to postscreen_denylist_action in Postfix 3.6.
4874 This feature is available in Postfix 2.8 - 3.5.
4876
4878 The amount of time between postscreen(8) cache cleanup runs. Cache
4879 cleanup increases the load on the cache database and should therefore
4880 not be run frequently. This feature requires that the cache database
4881 supports the "delete" and "sequence" operators. Specify a zero inter‐
4882 val to disable cache cleanup.
4883 After each cache cleanup run, the postscreen(8) daemon logs the number
4885 of entries that were retained and dropped. A cleanup run is logged as
4886 "partial" when the daemon terminates early after "postfix reload",
4887 "postfix stop", or no requests for $max_idle seconds.
4888 Time units: s (seconds), m (minutes), h (hours), d (days), w (weeks).
4890 This feature is available in Postfix 2.8.
4892
4894 Persistent storage for the postscreen(8) server decisions.
4895 To share a postscreen(8) cache between multiple postscreen(8) in‐
4897 stances, use "postscreen_cache_map = proxy:btree:/path/to/file". This
4898 requires Postfix version 2.9 or later; earlier proxymap(8) implementa‐
4899 tions don't support cache cleanup. For an alternative approach see the
4900 memcache_table(5) manpage.
4901 This feature is available in Postfix 2.8.
4903
4905 The amount of time that postscreen(8) will cache an expired temporary
4906 allowlist entry before it is removed. This prevents clients from being
4907 logged as "NEW" just because their cache entry expired an hour ago. It
4908 also prevents the cache from filling up with clients that passed some
4909 deep protocol test once and never came back.
4910 Time units: s (seconds), m (minutes), h (hours), d (days), w (weeks).
4912 This feature is available in Postfix 2.8.
4914
4916 tion_count_limit)
4917 How many simultaneous connections any remote SMTP client is allowed to
4918 have with the postscreen(8) daemon. By default, this limit is the same
4919 as with the Postfix SMTP server. Note that the triage process can take
4920 several seconds, with the time spent in postscreen_greet_wait delay,
4921 and with the time spent talking to the postscreen(8) built-in dummy
4922 SMTP protocol engine.
4923 This feature is available in Postfix 2.8.
4925
4927 The limit on the total number of commands per SMTP session for
4928 postscreen(8)'s built-in SMTP protocol engine. This SMTP engine defers
4929 or rejects all attempts to deliver mail, therefore there is no need to
4930 enforce separate limits on the number of junk commands and error com‐
4931 mands.
4932 This feature is available in Postfix 2.8.
4934
4936 A mechanism to transform commands from remote SMTP clients. See
4937 smtpd_command_filter for further details.
4938 This feature is available in Postfix 2.8 and later.
4940
4942 The time limit to read an entire command line with postscreen(8)'s
4943 built-in SMTP protocol engine.
4944 This feature is available in Postfix 2.8.
4946
4948 The action that postscreen(8) takes when a remote SMTP client is perma‐
4949 nently denylisted with the postscreen_access_list parameter. Specify
4950 one of the following:
4951 ignore (default)
4953 Ignore this result. Allow other tests to complete. Repeat this
4954 test the next time the client connects. This option is useful
4955 for testing and collecting statistics without blocking mail.
4956 enforce
4958 Allow other tests to complete. Reject attempts to deliver mail
4959 with a 550 SMTP reply, and log the helo/sender/recipient infor‐
4960 mation. Repeat this test the next time the client connects.
4961 drop Drop the connection immediately with a 521 SMTP reply. Repeat
4963 this test the next time the client connects.
4964 This feature is available in Postfix 3.6 and later.
4966 Available as postscreen_blacklist_action in Postfix 2.8 - 3.5.
4968
4970 Disable the SMTP VRFY command in the postscreen(8) daemon. See dis‐
4971 able_vrfy_command for details.
4972 This feature is available in Postfix 2.8.
4974
4976 card_ehlo_keyword_address_maps)
4977 Lookup tables, indexed by the remote SMTP client address, with case in‐
4978 sensitive lists of EHLO keywords (pipelining, starttls, auth, etc.)
4979 that the postscreen(8) server will not send in the EHLO response to a
4980 remote SMTP client. See smtpd_discard_ehlo_keywords for details. The
4981 table is not searched by hostname for robustness reasons.
4982 This feature is available in Postfix 2.8 and later.
4984
4986 A case insensitive list of EHLO keywords (pipelining, starttls, auth,
4987 etc.) that the postscreen(8) server will not send in the EHLO response
4988 to a remote SMTP client. See smtpd_discard_ehlo_keywords for details.
4989 This feature is available in Postfix 2.8 and later.
4991
4993 The action that postscreen(8) takes when a remote SMTP client's com‐
4994 bined DNSBL score is equal to or greater than a threshold (as defined
4995 with the postscreen_dnsbl_sites and postscreen_dnsbl_threshold parame‐
4996 ters). Specify one of the following:
4997 ignore (default)
4999 Ignore the failure of this test. Allow other tests to complete.
5000 Repeat this test the next time the client connects. This option
5001 is useful for testing and collecting statistics without blocking
5002 mail.
5003 enforce
5005 Allow other tests to complete. Reject attempts to deliver mail
5006 with a 550 SMTP reply, and log the helo/sender/recipient infor‐
5007 mation. Repeat this test the next time the client connects.
5008 drop Drop the connection immediately with a 521 SMTP reply. Repeat
5010 this test the next time the client connects.
5011 This feature is available in Postfix 2.8.
5013
5015 Allow a remote SMTP client to skip "before" and "after 220 greeting"
5016 protocol tests, based on its combined DNSBL score as defined with the
5017 postscreen_dnsbl_sites parameter.
5018 Specify a negative value to enable this feature. When a client passes
5020 the postscreen_dnsbl_allowlist_threshold without having failed other
5021 tests, all pending or disabled tests are flagged as completed with a
5022 time-to-live value equal to postscreen_dnsbl_ttl. When a test was al‐
5023 ready completed, its time-to-live value is updated if it was less than
5024 postscreen_dnsbl_ttl.
5025 This feature is available in Postfix 3.6 and later.
5027 Available as postscreen_dnsbl_whitelist_threshold in Postfix 2.11 -
5029 3.5.
5030
5032 ${postscreen_dnsbl_ttl?{$postscreen_dnsbl_ttl}:{1}}h)
5033 The maximum amount of time that postscreen(8) will use the result from
5034 a successful DNS-based reputation test before a client IP address is
5035 required to pass that test again. If the DNS reply specifies a shorter
5036 TTL value, that value will be used unless it would be smaller than
5037 postscreen_dnsbl_min_ttl.
5038 Specify a non-zero time value (an integral value plus an optional
5040 one-letter suffix that specifies the time unit). Time units: s (sec‐
5041 onds), m (minutes), h (hours), d (days), w (weeks).
5042 This feature is available in Postfix 3.1. The default setting is back‐
5044 wards-compatible with older Postfix versions.
5045
5047 The minimum amount of time that postscreen(8) will use the result from
5048 a successful DNS-based reputation test before a client IP address is
5049 required to pass that test again. If the DNS reply specifies a larger
5050 TTL value, that value will be used unless it would be larger than
5051 postscreen_dnsbl_max_ttl.
5052 Specify a non-zero time value (an integral value plus an optional
5054 one-letter suffix that specifies the time unit). Time units: s (sec‐
5055 onds), m (minutes), h (hours), d (days), w (weeks).
5056 This feature is available in Postfix 3.1.
5058
5060 A mapping from actual DNSBL domain name which includes a secret pass‐
5061 word, to the DNSBL domain name that postscreen will reply with when it
5062 rejects mail. When no mapping is found, the actual DNSBL domain will
5063 be used.
5064 For maximal stability it is best to use a file that is read into memory
5066 such as pcre:, regexp: or texthash: (texthash: is similar to hash:, ex‐
5067 cept a) there is no need to run postmap(1) before the file can be used,
5068 and b) texthash: does not detect changes after the file is read).
5069 Example:
5071 /etc/postfix/main.cf:
5073 postscreen_dnsbl_reply_map = texthash:/etc/postfix/dnsbl_reply
5074 /etc/postfix/dnsbl_reply:
5076 secret.zen.spamhaus.org zen.spamhaus.org
5077 This feature is available in Postfix 2.8.
5079
5081 Optional list of DNS allow/denylist domains, filters and weight fac‐
5082 tors. When the list is non-empty, the dnsblog(8) daemon will query
5083 these domains with the IP addresses of remote SMTP clients, and
5084 postscreen(8) will update an SMTP client's DNSBL score with each
5085 non-error reply.
5086 Caution: when postscreen rejects mail, it replies with the DNSBL domain
5088 name. Use the postscreen_dnsbl_reply_map feature to hide "password" in‐
5089 formation in DNSBL domain names.
5090 When a client's score is equal to or greater than the threshold speci‐
5092 fied with postscreen_dnsbl_threshold, postscreen(8) can drop the con‐
5093 nection with the remote SMTP client.
5094 Specify a list of domain=filter*weight entries, separated by comma or
5096 whitespace.
5097 • When no "=filter" is specified, postscreen(8) will use any
5099 non-error DNSBL reply. Otherwise, postscreen(8) uses only DNSBL
5100 replies that match the filter. The filter has the form d.d.d.d,
5101 where each d is a number, or a pattern inside [] that contains
5102 one or more ";"-separated numbers or number..number ranges.
5103 • When no "*weight" is specified, postscreen(8) increments the re‐
5105 mote SMTP client's DNSBL score by 1. Otherwise, the weight must
5106 be an integral number, and postscreen(8) adds the specified
5107 weight to the remote SMTP client's DNSBL score. Specify a nega‐
5108 tive number for allowlisting.
5109 • When one postscreen_dnsbl_sites entry produces multiple DNSBL
5111 responses, postscreen(8) applies the weight at most once.
5112 Examples:
5114 To use example.com as a high-confidence blocklist, and to block mail
5116 with example.net and example.org only when both agree:
5117 postscreen_dnsbl_threshold = 2
5119 postscreen_dnsbl_sites = example.com*2, example.net, example.org
5120 To filter only DNSBL replies containing 127.0.0.4:
5122 postscreen_dnsbl_sites = example.com=127.0.0.4
5124 This feature is available in Postfix 2.8.
5126
5128 The inclusive lower bound for blocking a remote SMTP client, based on
5129 its combined DNSBL score as defined with the postscreen_dnsbl_sites pa‐
5130 rameter.
5131 This feature is available in Postfix 2.8.
5133
5135 The time limit for DNSBL or DNSWL lookups. This is separate from the
5136 timeouts in the dnsblog(8) daemon which are defined by system re‐
5137 solver(3) routines.
5138 This feature is available in Postfix 3.0.
5140
5142 The amount of time that postscreen(8) will use the result from a suc‐
5143 cessful DNS-based reputation test before a client IP address is re‐
5144 quired to pass that test again.
5145 Specify a non-zero time value (an integral value plus an optional
5147 one-letter suffix that specifies the time unit). Time units: s (sec‐
5148 onds), m (minutes), h (hours), d (days), w (weeks).
5149 This feature is available in Postfix 2.8-3.0. It was replaced by
5151 postscreen_dnsbl_max_ttl in Postfix 3.1.
5152
5154 Renamed to postscreen_dnsbl_allowlist_threshold in Postfix 3.6.
5155 This feature is available in Postfix 2.11 - 3.5.
5157
5159 Mandatory TLS: announce STARTTLS support to remote SMTP clients, and
5160 require that clients use TLS encryption. See smtpd_postscreen_en‐
5161 force_tls for details.
5162 This feature is available in Postfix 2.8 and later. Preferably, use
5164 postscreen_tls_security_level instead.
5165
5167 List of characters that are permitted in postscreen_reject_footer at‐
5168 tribute expansions. See smtpd_expansion_filter for further details.
5169 This feature is available in Postfix 2.8 and later.
5171
5173 List of commands that the postscreen(8) server considers in violation
5174 of the SMTP protocol. See smtpd_forbidden_commands for syntax, and
5175 postscreen_non_smtp_command_action for possible actions.
5176 This feature is available in Postfix 2.8.
5178
5180 The action that postscreen(8) takes when a remote SMTP client speaks
5181 before its turn within the time specified with the
5182 postscreen_greet_wait parameter. Specify one of the following:
5183 ignore (default)
5185 Ignore the failure of this test. Allow other tests to complete.
5186 Repeat this test the next time the client connects. This option
5187 is useful for testing and collecting statistics without blocking
5188 mail.
5189 enforce
5191 Allow other tests to complete. Reject attempts to deliver mail
5192 with a 550 SMTP reply, and log the helo/sender/recipient infor‐
5193 mation. Repeat this test the next time the client connects.
5194 drop Drop the connection immediately with a 521 SMTP reply. Repeat
5196 this test the next time the client connects.
5197 In either case, postscreen(8) will not allowlist the remote SMTP client
5199 IP address.
5200 This feature is available in Postfix 2.8.
5202
5204 The text in the optional "220-text..." server response that
5205 postscreen(8) sends ahead of the real Postfix SMTP server's "220
5206 text..." response, in an attempt to confuse bad SMTP clients so that
5207 they speak before their turn (pre-greet). Specify an empty value to
5208 disable this feature.
5209 This feature is available in Postfix 2.8.
5211
5213 The amount of time that postscreen(8) will use the result from a suc‐
5214 cessful PREGREET test. During this time, the client IP address is ex‐
5215 cluded from this test. The default is relatively short, because a good
5216 client can immediately talk to a real Postfix SMTP server.
5217 Specify a non-zero time value (an integral value plus an optional
5219 one-letter suffix that specifies the time unit). Time units: s (sec‐
5220 onds), m (minutes), h (hours), d (days), w (weeks).
5221 This feature is available in Postfix 2.8.
5223
5225 The amount of time that postscreen(8) will wait for an SMTP client to
5226 send a command before its turn, and for DNS blocklist lookup results to
5227 arrive (default: up to 2 seconds under stress, up to 6 seconds other‐
5228 wise).
5229 Specify a non-zero time value (an integral value plus an optional
5231 one-letter suffix that specifies the time unit).
5232 Time units: s (seconds), m (minutes), h (hours), d (days), w (weeks).
5234 This feature is available in Postfix 2.8.
5236
5238 Require that a remote SMTP client sends HELO or EHLO before commencing
5239 a MAIL transaction.
5240 This feature is available in Postfix 2.8.
5242
5244 The action that postscreen(8) takes when a remote SMTP client sends
5245 non-SMTP commands as specified with the postscreen_forbidden_commands
5246 parameter. Specify one of the following:
5247 ignore Ignore the failure of this test. Allow other tests to complete.
5249 Do not repeat this test before some the result from some other
5250 test expires. This option is useful for testing and collecting
5251 statistics without blocking mail permanently.
5252 enforce
5254 Allow other tests to complete. Reject attempts to deliver mail
5255 with a 550 SMTP reply, and log the helo/sender/recipient infor‐
5256 mation. Repeat this test the next time the client connects.
5257 drop Drop the connection immediately with a 521 SMTP reply. Repeat
5259 this test the next time the client connects. This action is the
5260 same as with the Postfix SMTP server's smtpd_forbidden_commands
5261 feature.
5262 This feature is available in Postfix 2.8.
5264
5266 Enable "non-SMTP command" tests in the postscreen(8) server. These
5267 tests are expensive: a client must disconnect after it passes the test,
5268 before it can talk to a real Postfix SMTP server.
5269 This feature is available in Postfix 2.8.
5271
5273 The amount of time that postscreen(8) will use the result from a suc‐
5274 cessful "non_smtp_command" SMTP protocol test. During this time, the
5275 client IP address is excluded from this test. The default is long be‐
5276 cause a client must disconnect after it passes the test, before it can
5277 talk to a real Postfix SMTP server.
5278 Specify a non-zero time value (an integral value plus an optional
5280 one-letter suffix that specifies the time unit). Time units: s (sec‐
5281 onds), m (minutes), h (hours), d (days), w (weeks).
5282 This feature is available in Postfix 2.8.
5284
5286 The action that postscreen(8) takes when a remote SMTP client sends
5287 multiple commands instead of sending one command and waiting for the
5288 server to respond. Specify one of the following:
5289 ignore Ignore the failure of this test. Allow other tests to complete.
5291 Do not repeat this test before some the result from some other
5292 test expires. This option is useful for testing and collecting
5293 statistics without blocking mail permanently.
5294 enforce
5296 Allow other tests to complete. Reject attempts to deliver mail
5297 with a 550 SMTP reply, and log the helo/sender/recipient infor‐
5298 mation. Repeat this test the next time the client connects.
5299 drop Drop the connection immediately with a 521 SMTP reply. Repeat
5301 this test the next time the client connects.
5302 This feature is available in Postfix 2.8.
5304
5306 Enable "pipelining" SMTP protocol tests in the postscreen(8) server.
5307 These tests are expensive: a good client must disconnect after it
5308 passes the test, before it can talk to a real Postfix SMTP server.
5309 This feature is available in Postfix 2.8.
5311
5313 The amount of time that postscreen(8) will use the result from a suc‐
5314 cessful "pipelining" SMTP protocol test. During this time, the client
5315 IP address is excluded from this test. The default is long because a
5316 good client must disconnect after it passes the test, before it can
5317 talk to a real Postfix SMTP server.
5318 Specify a non-zero time value (an integral value plus an optional
5320 one-letter suffix that specifies the time unit). Time units: s (sec‐
5321 onds), m (minutes), h (hours), d (days), w (weeks).
5322 This feature is available in Postfix 2.8.
5324
5326 The number of clients that can be waiting for service from a real Post‐
5327 fix SMTP server process. When this queue is full, all clients will re‐
5328 ceive a 421 response.
5329 This feature is available in Postfix 2.8.
5331
5333 The number of non-allowlisted clients that can be waiting for a deci‐
5334 sion whether they will receive service from a real Postfix SMTP server
5335 process. When this queue is full, all non-allowlisted clients will re‐
5336 ceive a 421 response.
5337 This feature is available in Postfix 2.8.
5339
5341 Optional information that is appended after a 4XX or 5XX postscreen(8)
5342 server response. See smtpd_reject_footer for further details.
5343 This feature is available in Postfix 2.8 and later.
5345
5347 Optional lookup table for information that is appended after a 4XX or
5348 5XX postscreen(8) server response. See smtpd_reject_footer_maps for
5349 further details.
5350 This feature is available in Postfix 3.4 and later.
5352
5354 The SMTP TLS security level for the postscreen(8) server; when a
5355 non-empty value is specified, this overrides the obsolete parameters
5356 postscreen_use_tls and postscreen_enforce_tls. See smtpd_tls_secu‐
5357 rity_level for details.
5358 This feature is available in Postfix 2.8 and later.
5360
5362 The name of the proxy protocol used by an optional before-postscreen
5363 proxy agent. When a proxy agent is used, this protocol conveys local
5364 and remote address and port information. Specify "postscreen_up‐
5365 stream_proxy_protocol = haproxy" to enable the haproxy protocol; ver‐
5366 sion 2 is supported with Postfix 3.5 and later.
5367 This feature is available in Postfix 2.10 and later.
5369
5371 The time limit for the proxy protocol specified with the postscreen_up‐
5372 stream_proxy_protocol parameter.
5373 This feature is available in Postfix 2.10 and later.
5375
5377 Opportunistic TLS: announce STARTTLS support to remote SMTP clients,
5378 but do not require that clients use TLS encryption.
5379 This feature is available in Postfix 2.8 and later. Preferably, use
5381 postscreen_tls_security_level instead.
5382
5384 How much time a postscreen(8) process may take to respond to a remote
5385 SMTP client command or to perform a cache operation before it is termi‐
5386 nated by a built-in watchdog timer. This is a safety mechanism that
5387 prevents postscreen(8) from becoming non-responsive due to a bug in
5388 Postfix itself or in system software. To avoid false alarms and unnec‐
5389 essary cache corruption this limit cannot be set under 10s.
5390 Specify a non-zero time value (an integral value plus an optional
5392 one-letter suffix that specifies the time unit). Time units: s (sec‐
5393 onds), m (minutes), h (hours), d (days), w (weeks).
5394 This feature is available in Postfix 2.8.
5396
5398 Renamed to postscreen_allowlist_interfaces in Postfix 3.6.
5399 This feature is available in Postfix 2.9 - 3.5.
5401
5403 The message delivery contexts where the Postfix local(8) delivery agent
5404 prepends a Delivered-To: message header with the address that the mail
5405 was delivered to. This information is used for mail delivery loop de‐
5406 tection.
5407 By default, the Postfix local delivery agent prepends a Delivered-To:
5409 header when forwarding mail and when delivering to file (mailbox) and
5410 command. Turning off the Delivered-To: header when forwarding mail is
5411 not recommended.
5412 Specify zero or more of forward, file, or command.
5414 Example:
5416 prepend_delivered_header = forward
5418
5420 The process ID of a Postfix command or daemon process.
5421
5423 The location of Postfix PID files relative to $queue_directory. This
5424 is a read-only parameter.
5425
5427 The process name of a Postfix command or daemon process.
5428
5430 What address lookup tables copy an address extension from the lookup
5431 key to the lookup result.
5432 For example, with a virtual(5) mapping of "joe@example.com =>
5434 joe.user@example.net", the address "joe+foo@example.com" would rewrite
5435 to "joe.user+foo@example.net".
5436 Specify zero or more of canonical, virtual, alias, forward, include or
5438 generic. These cause address extension propagation with canonical(5),
5439 virtual(5), and aliases(5) maps, with local(8) .forward and :include:
5440 file lookups, and with smtp(8) generic maps, respectively.
5441 Note: enabling this feature for types other than canonical and virtual
5443 is likely to cause problems when mail is forwarded to other sites, es‐
5444 pecially with mail that is sent to a mailing list exploder address.
5445 Examples:
5447 propagate_unmatched_extensions = canonical, virtual, alias,
5449 forward, include
5450 propagate_unmatched_extensions = canonical, virtual
5451
5453 The network interface addresses that this mail system receives mail on
5454 by way of a proxy or network address translation unit.
5455 This feature is available in Postfix 2.0 and later.
5457 You must specify your "outside" proxy/NAT addresses when your system is
5459 a backup MX host for other domains, otherwise mail delivery loops will
5460 happen when the primary MX host is down.
5461 Example:
5463 proxy_interfaces = 1.2.3.4
5465
5467 The lookup tables that the proxymap(8) server is allowed to access for
5468 the read-only service.
5469 Specify zero or more "type:name" lookup tables, separated by whitespace
5471 or comma. Table references that don't begin with proxy: are ignored.
5472 This feature is available in Postfix 2.0 and later.
5474
5476 The lookup tables that the proxymap(8) server is allowed to access for
5477 the read-write service. Postfix-owned local database files should be
5478 stored under the Postfix-owned data_directory. Table references that
5479 don't begin with proxy: are ignored.
5480 This feature is available in Postfix 2.5 and later.
5482
5484 The name of the proxymap read-only table lookup service. This service
5485 is normally implemented by the proxymap(8) daemon.
5486 This feature is available in Postfix 2.6 and later.
5488
5490 The name of the proxywrite read-write table lookup service. This ser‐
5491 vice is normally implemented by the proxymap(8) daemon.
5492 This feature is available in Postfix 2.6 and later.
5494
5496 The minimal delay between warnings that a specific destination is clog‐
5497 ging up the Postfix active queue. Specify 0 to disable.
5498 This feature is enabled with the helpful_warnings parameter.
5500 This feature is available in Postfix 2.0 and later.
5502
5504 How much time a Postfix queue manager process may take to handle a re‐
5505 quest before it is terminated by a built-in watchdog timer.
5506 Time units: s (seconds), m (minutes), h (hours), d (days), w (weeks).
5508 The default time unit is s (seconds).
5509 This feature is available in Postfix 2.8 and later.
5511
5513 Obsolete feature: the percentage of delivery resources that a busy mail
5514 system will use up for delivery of a large mailing list message.
5515 This feature exists only in the oqmgr(8) old queue manager. The current
5517 queue manager solves the problem in a better way.
5518
5520 The time limit for the queue manager to send or receive information
5521 over an internal communication channel. The purpose is to break out of
5522 deadlock situations. If the time limit is exceeded the software either
5523 retries or aborts the operation.
5524 Time units: s (seconds), m (minutes), h (hours), d (days), w (weeks).
5526 The default time unit is s (seconds).
5527 This feature is available in Postfix 2.8 and later.
5529
5531 The maximal number of messages in the active queue.
5532
5534 The maximal number of recipients held in memory by the Postfix queue
5535 manager, and the maximal size of the short-term, in-memory "dead" des‐
5536 tination status cache.
5537
5539 The minimal number of in-memory recipients for any message. This takes
5540 priority over any other in-memory recipient limits (i.e., the global
5541 qmgr_message_recipient_limit and the per transport _recipient_limit) if
5542 necessary. The minimum value allowed for this parameter is 1.
5543
5545 What remote QMQP clients are allowed to connect to the Postfix QMQP
5546 server port.
5547 By default, no client is allowed to use the service. This is because
5549 the QMQP server will relay mail to any destination.
5550 Specify a list of client patterns. A list pattern specifies a host
5552 name, a domain name, an internet address, or a network/mask pattern,
5553 where the mask specifies the number of bits in the network part. When
5554 a pattern specifies a file name, its contents are substituted for the
5555 file name; when a pattern is a "type:table" table specification, table
5556 lookup is used instead.
5557 Patterns are separated by whitespace and/or commas. In order to reverse
5559 the result, precede a pattern with an exclamation point (!). The form
5560 "!/file/name" is supported only in Postfix version 2.4 and later.
5561 Pattern matching of domain names is controlled by the presence or ab‐
5563 sence of "qmqpd_authorized_clients" in the parent_domain_matches_subdo‐
5564 mains parameter value.
5565 Example:
5567 qmqpd_authorized_clients = !192.168.0.1, 192.168.0.0/24
5569
5571 Enable logging of the remote QMQP client port in addition to the host‐
5572 name and IP address. The logging format is "host[address]:port".
5573 This feature is available in Postfix 2.5 and later.
5575
5577 How long the Postfix QMQP server will pause before sending a negative
5578 reply to the remote QMQP client. The purpose is to slow down confused
5579 or malicious clients.
5580 Time units: s (seconds), m (minutes), h (hours), d (days), w (weeks).
5582 The default time unit is s (seconds).
5583
5585 The time limit for sending or receiving information over the network.
5586 If a read or write operation blocks for more than $qmqpd_timeout sec‐
5587 onds the Postfix QMQP server gives up and disconnects.
5588 Time units: s (seconds), m (minutes), h (hours), d (days), w (weeks).
5590 The default time unit is s (seconds).
5591
5593 The location of the Postfix top-level queue directory. This is the root
5594 directory of Postfix daemon processes that run chrooted.
5595
5597 The maximal number of (name=value) attributes that may be stored in a
5598 Postfix queue file. The limit is enforced by the cleanup(8) server.
5599 This feature is available in Postfix 2.0 and later.
5601
5603 The minimal amount of free space in bytes in the queue file system that
5604 is needed to receive mail. This is currently used by the Postfix SMTP
5605 server to decide if it will accept any mail at all.
5606 By default, the Postfix SMTP server rejects MAIL FROM commands when the
5608 amount of free space is less than 1.5*$message_size_limit (Postfix ver‐
5609 sion 2.1 and later). To specify a higher minimum free space limit,
5610 specify a queue_minfree value that is at least 1.5*$message_size_limit.
5611 With Postfix versions 2.0 and earlier, a queue_minfree value of zero
5613 means there is no minimum required amount of free space.
5614
5616 The time between deferred queue scans by the queue manager; prior to
5617 Postfix 2.4 the default value was 1000s.
5618 This parameter should be set less than or equal to $minimal_back‐
5620 off_time. See also $maximal_backoff_time.
5621 Time units: s (seconds), m (minutes), h (hours), d (days), w (weeks).
5623 The default time unit is s (seconds).
5624
5626 The name of the qmgr(8) service. This service manages the Postfix queue
5627 and schedules delivery requests.
5628 This feature is available in Postfix 2.0 and later.
5630
5632 Optional lookup tables with RBL response templates. The tables are in‐
5633 dexed by the RBL domain name. By default, Postfix uses the default tem‐
5634 plate as specified with the default_rbl_reply configuration parameter.
5635 See there for a discussion of the syntax of RBL reply templates.
5636 This feature is available in Postfix 2.0 and later.
5638
5640 The location of Postfix README files that describe how to build, con‐
5641 figure or operate a specific Postfix subsystem or feature.
5642
5644 Enable or disable recipient validation, built-in content filtering, or
5645 address mapping. Typically, these are specified in master.cf as com‐
5646 mand-line arguments for the smtpd(8), qmqpd(8) or pickup(8) daemons.
5647 Specify zero or more of the following options. The options override
5649 main.cf settings and are either implemented by smtpd(8), qmqpd(8), or
5650 pickup(8) themselves, or they are forwarded to the cleanup server.
5651 no_unknown_recipient_checks
5653 Do not try to reject unknown recipients (SMTP server only).
5654 This is typically specified AFTER an external content filter.
5655 no_address_mappings
5657 Disable canonical address mapping, virtual alias map expansion,
5658 address masquerading, and automatic BCC (blind carbon-copy) re‐
5659 cipients. This is typically specified BEFORE an external content
5660 filter.
5661 no_header_body_checks
5663 Disable header/body_checks. This is typically specified AFTER an
5664 external content filter.
5665 no_milters
5667 Disable Milter (mail filter) applications. This is typically
5668 specified AFTER an external content filter.
5669 Note: when the "BEFORE content filter" receive_override_options setting
5671 is specified in the main.cf file, specify the "AFTER content filter"
5672 receive_override_options setting in master.cf (and vice versa).
5673 Examples:
5675 receive_override_options =
5677 no_unknown_recipient_checks, no_header_body_checks
5678 receive_override_options = no_address_mappings
5679 This feature is available in Postfix 2.1 and later.
5681
5683 Optional BCC (blind carbon-copy) address lookup tables, indexed by re‐
5684 cipient address. The BCC address (multiple results are not supported)
5685 is added when mail enters from outside of Postfix.
5686 Specify zero or more "type:name" lookup tables, separated by whitespace
5688 or comma. Tables will be searched in the specified order until a match
5689 is found.
5690 The table search order is as follows:
5692 • Look up the "user+extension@domain.tld" address including the
5694 optional address extension.
5695 • Look up the "user@domain.tld" address without the optional ad‐
5697 dress extension.
5698 • Look up the "user+extension" address local part when the recipi‐
5700 ent domain equals $myorigin, $mydestination, $inet_interfaces or
5701 $proxy_interfaces.
5702 • Look up the "user" address local part when the recipient domain
5704 equals $myorigin, $mydestination, $inet_interfaces or $proxy_in‐
5705 terfaces.
5706 • Look up the "@domain.tld" part.
5708 Note: with Postfix 2.3 and later the BCC address is added as if it was
5710 specified with NOTIFY=NONE. The sender will not be notified when the
5711 BCC address is undeliverable, as long as all down-stream software im‐
5712 plements RFC 3461.
5713 Note: with Postfix 2.2 and earlier the sender will unconditionally be
5715 notified when the BCC address is undeliverable.
5716 Note: automatic BCC recipients are produced only for new mail. To
5718 avoid mailer loops, automatic BCC recipients are not generated after
5719 Postfix forwards mail internally, or after Postfix generates mail it‐
5720 self.
5721 Example:
5723 recipient_bcc_maps = hash:/etc/postfix/recipient_bcc
5725 After a change, run "postmap /etc/postfix/recipient_bcc".
5727 This feature is available in Postfix 2.1 and later.
5729
5731 What addresses are subject to recipient_canonical_maps address mapping.
5732 By default, recipient_canonical_maps address mapping is applied to en‐
5733 velope recipient addresses, and to header recipient addresses.
5734 Specify one or more of: envelope_recipient, header_recipient
5736 This feature is available in Postfix 2.2 and later.
5738
5740 Optional address mapping lookup tables for envelope and header recipi‐
5741 ent addresses. The table format and lookups are documented in canoni‐
5742 cal(5).
5743 Note: $recipient_canonical_maps is processed before $canonical_maps.
5745 Example:
5747 recipient_canonical_maps = hash:/etc/postfix/recipient_canonical
5749
5751 The set of characters that can separate an email address localpart,
5752 user name, or a .forward file name from its extension. For example,
5753 with "recipient_delimiter = +", the software tries user+foo@example.com
5754 before trying user@example.com, user+foo before trying user, and .for‐
5755 ward+foo before trying .forward.
5756 More formally, an email address localpart or user name is separated
5758 from its extension by the first character that matches the recipi‐
5759 ent_delimiter set. The delimiter character and extension may then be
5760 used to generate an extended .forward file name. This implementation
5761 recognizes one delimiter character and one extension per email address
5762 localpart or email address. With Postfix 2.10 and earler, the recipi‐
5763 ent_delimiter specifies a single character.
5764 See canonical(5), local(8), relocated(5) and virtual(5) for the effects
5766 of recipient_delimiter on lookups in aliases, canonical, virtual, and
5767 relocated maps, and see the propagate_unmatched_extensions parameter
5768 for propagating an extension from one email address to another.
5769 When used in command_execution_directory, forward_path, or luser_relay,
5771 ${recipient_delimiter} is replaced with the actual recipient delimiter
5772 that was found in the recipient email address (Postfix 2.11 and later),
5773 or it is replaced with the main.cf recipient_delimiter parameter value
5774 (Postfix 2.10 and earlier).
5775 The recipient_delimiter is not applied to the mailer-daemon address,
5777 the postmaster address, or the double-bounce address. With the default
5778 "owner_request_special = yes" setting, the recipient_delimiter is also
5779 not applied to addresses with the special "owner-" prefix or the spe‐
5780 cial "-request" suffix.
5781 Examples:
5783 # Handle Postfix-style extensions.
5785 recipient_delimiter = +
5786 # Handle both Postfix and qmail extensions (Postfix 2.11 and later).
5788 recipient_delimiter = +-
5789 # Use .forward for mail without address extension, and for mail with
5791 # an unrecognized address extension.
5792 forward_path = $home/.forward${recipient_delimiter}${extension},
5793 $home/.forward
5794
5796 The numerical Postfix SMTP server response code when a remote SMTP
5797 client request is rejected by the "reject" restriction.
5798 Do not change this unless you have a complete understanding of RFC
5800 5321.
5801
5803 The Postfix SMTP server's action when a reject-type restriction fails
5804 due to a temporary error condition. Specify "defer" to defer the remote
5805 SMTP client request immediately. With the default "defer_if_permit" ac‐
5806 tion, the Postfix SMTP server continues to look for opportunities to
5807 reject mail, and defers the client request only if it would otherwise
5808 be accepted.
5809 For finer control, see: unverified_recipient_tempfail_action, unveri‐
5811 fied_sender_tempfail_action, unknown_address_tempfail_action, and un‐
5812 known_helo_hostname_tempfail_action.
5813 This feature is available in Postfix 2.6 and later.
5815
5817 List of tables with remote SMTP client-certificate fingerprints or pub‐
5818 lic key fingerprints (Postfix 2.9 and later) for which the Postfix SMTP
5819 server will allow access with the permit_tls_clientcerts feature. The
5820 fingerprint digest algorithm is configurable via the smtpd_tls_finger‐
5821 print_digest parameter (hard-coded as md5 prior to Postfix version
5822 2.5).
5823 The default algorithm is sha256 with Postfix >= 3.6 and the compatibil‐
5825 ity_level set to 3.6 or higher. With Postfix <= 3.5, the default algo‐
5826 rithm is md5. The best-practice algorithm is now sha256. Recent ad‐
5827 vances in hash function cryptanalysis have led to md5 and sha1 being
5828 deprecated in favor of sha256. However, as long as there are no known
5829 "second pre-image" attacks against the older algorithms, their use in
5830 this context, though not recommended, is still likely safe.
5831 Postfix lookup tables are in the form of (key, value) pairs. Since we
5833 only need the key, the value can be chosen freely, e.g. the name of
5834 the user or host: D7:04:2F:A7:0B:8C:A5:21:FA:31:77:E1:41:8A:EE:80
5835 lutzpc.at.home
5836 Example:
5838 relay_clientcerts = hash:/etc/postfix/relay_clientcerts
5840 For more fine-grained control, use check_ccert_access to select an ap‐
5842 propriate access(5) policy for each client. See RESTRIC‐
5843 TION_CLASS_README.
5844 This feature is available with Postfix version 2.2.
5846
5848 rency_limit)
5849 The maximal number of parallel deliveries to the same destination via
5850 the relay message delivery transport. This limit is enforced by the
5851 queue manager. The message delivery transport name is the first field
5852 in the entry in the master.cf file.
5853 This feature is available in Postfix 2.0 and later.
5855
5857 ent_limit)
5858 The maximal number of recipients per message for the relay message de‐
5859 livery transport. This limit is enforced by the queue manager. The mes‐
5860 sage delivery transport name is the first field in the entry in the
5861 master.cf file.
5862 Setting this parameter to a value of 1 changes the meaning of re‐
5864 lay_destination_concurrency_limit from concurrency per domain into con‐
5865 currency per recipient.
5866 This feature is available in Postfix 2.0 and later.
5868
5870 What destination domains (and subdomains thereof) this system will re‐
5871 lay mail to. For details about how the relay_domains value is used, see
5872 the description of the permit_auth_destination and reject_unauth_desti‐
5873 nation SMTP recipient restrictions.
5874 Domains that match $relay_domains are delivered with the $relay_trans‐
5876 port mail delivery transport. The SMTP server validates recipient ad‐
5877 dresses with $relay_recipient_maps and rejects non-existent recipients.
5878 See also the relay domains address class in the ADDRESS_CLASS_README
5879 file.
5880 Note: Postfix will not automatically forward mail for domains that list
5882 this system as their primary or backup MX host. See the per‐
5883 mit_mx_backup restriction in the postconf(5) manual page.
5884 Specify a list of host or domain names, "/file/name" patterns or
5886 "type:table" lookup tables, separated by commas and/or whitespace.
5887 Continue long lines by starting the next line with whitespace. A
5888 "/file/name" pattern is replaced by its contents; a "type:table" lookup
5889 table is matched when a (parent) domain appears as lookup key. Specify
5890 "!pattern" to exclude a domain from the list. The form "!/file/name" is
5891 supported only in Postfix version 2.4 and later.
5892 Pattern matching of domain names is controlled by the presence or ab‐
5894 sence of "relay_domains" in the parent_domain_matches_subdomains param‐
5895 eter value.
5896
5898 The numerical Postfix SMTP server response code when a client request
5899 is rejected by the reject_unauth_destination recipient restriction.
5900 Do not change this unless you have a complete understanding of RFC
5902 5321.
5903
5905 Optional lookup tables with all valid addresses in the domains that
5906 match $relay_domains. Specify @domain as a wild-card for domains that
5907 have no valid recipient list, and become a source of backscatter mail:
5908 Postfix accepts spam for non-existent recipients and then floods inno‐
5909 cent people with undeliverable mail. Technically, tables listed with
5910 $relay_recipient_maps are used as lists: Postfix needs to know only if
5911 a lookup string is found or not, but it does not use the result from
5912 table lookup.
5913 Specify zero or more "type:name" lookup tables, separated by whitespace
5915 or comma. Tables will be searched in the specified order until a match
5916 is found.
5917 If this parameter is non-empty, then the Postfix SMTP server will re‐
5919 ject mail to unknown relay users. This feature is off by default.
5920 See also the relay domains address class in the ADDRESS_CLASS_README
5922 file.
5923 Example:
5925 relay_recipient_maps = hash:/etc/postfix/relay_recipients
5927 This feature is available in Postfix 2.0 and later.
5929
5931 The default mail delivery transport and next-hop destination for remote
5932 delivery to domains listed with $relay_domains. In order of decreasing
5933 precedence, the nexthop destination is taken from $relay_transport,
5934 $sender_dependent_relayhost_maps, $relayhost, or from the recipient do‐
5935 main. This information can be overruled with the transport(5) table.
5936 Specify a string of the form transport:nexthop, where transport is the
5938 name of a mail delivery transport defined in master.cf. The :nexthop
5939 destination is optional; its syntax is documented in the manual page of
5940 the corresponding delivery agent.
5941 See also the relay domains address class in the ADDRESS_CLASS_README
5943 file.
5944 This feature is available in Postfix 2.0 and later.
5946
5948 The next-hop destination(s) for non-local mail; overrides non-local do‐
5949 mains in recipient addresses. This information is overruled with re‐
5950 lay_transport, sender_dependent_default_transport_maps, default_trans‐
5951 port, sender_dependent_relayhost_maps and with the transport(5) table.
5952 On an intranet, specify the organizational domain name. If your inter‐
5954 nal DNS uses no MX records, specify the name of the intranet gateway
5955 host instead.
5956 In the case of SMTP or LMTP delivery, specify one or more destinations
5958 in the form of a domain name, hostname, hostname:port, [hostname]:port,
5959 [hostaddress] or [hostaddress]:port, separated by comma or whitespace.
5960 The form [hostname] turns off MX lookups. Multiple destinations are
5961 supported in Postfix 3.5 and later.
5962 If you're connected via UUCP, see the UUCP_README file for useful in‐
5964 formation.
5965 Examples:
5967 relayhost = $mydomain
5969 relayhost = [gateway.example.com]
5970 relayhost = mail1.example:587, mail2.example:587
5971 relayhost = [an.ip.add.ress]
5972
5974 Optional lookup tables with new contact information for users or do‐
5975 mains that no longer exist. The table format and lookups are docu‐
5976 mented in relocated(5).
5977 Specify zero or more "type:name" lookup tables, separated by whitespace
5979 or comma. Tables will be searched in the specified order until a match
5980 is found.
5981 If you use this feature, run "postmap /etc/postfix/relocated" to build
5983 the necessary DBM or DB file after change, then "postfix reload" to
5984 make the changes visible.
5985 Examples:
5987 relocated_maps = dbm:/etc/postfix/relocated
5989 relocated_maps = hash:/etc/postfix/relocated
5990
5992 Don't rewrite message headers from remote clients at all when this pa‐
5993 rameter is empty; otherwise, rewrite message headers and append the
5994 specified domain name to incomplete addresses. The local_header_re‐
5995 write_clients parameter controls what clients Postfix considers local.
5996 Examples:
5998 The safe setting: append "domain.invalid" to incomplete header ad‐
6000 dresses from remote SMTP clients, so that those addresses cannot be
6001 confused with local addresses.
6002 remote_header_rewrite_domain = domain.invalid
6004 The default, purist, setting: don't rewrite headers from remote clients
6006 at all.
6007 remote_header_rewrite_domain =
6009
6011 Require that a local(8) recipient's home directory exists before mail
6012 delivery is attempted. By default this test is disabled. It can be
6013 useful for environments that import home directories to the mail server
6014 (IMPORTING HOME DIRECTORIES IS NOT RECOMMENDED).
6015
6017 Reset the local(8) delivery agent's idea of the owner-alias attribute,
6018 when delivering mail to a child alias that does not have its own owner
6019 alias.
6020 This feature is available in Postfix 2.8 and later. With older Postfix
6022 releases, the behavior is as if this parameter is set to "yes".
6023 As documented in aliases(5), when an alias name has a companion alias
6025 named owner-name, this will replace the envelope sender address, so
6026 that delivery errors will be reported to the owner alias instead of the
6027 sender. This configuration is recommended for mailing lists.
6028 A less known property of the owner alias is that it also forces the lo‐
6030 cal(8) delivery agent to write local and remote addresses from alias
6031 expansion to a new queue file, instead of attempting to deliver mail to
6032 local addresses as soon as they come out of alias expansion.
6033 Writing local addresses from alias expansion to a new queue file allows
6035 for robust handling of temporary delivery errors: errors with one local
6036 member have no effect on deliveries to other members of the list. On
6037 the other hand, delivery to local addresses as soon as they come out of
6038 alias expansion is fragile: a temporary error with one local address
6039 from alias expansion will cause the entire alias to be expanded repeat‐
6040 edly until the error goes away, or until the message expires in the
6041 queue. In that case, a problem with one list member results in multi‐
6042 ple message deliveries to other list members.
6043 The default behavior of Postfix 2.8 and later is to keep the
6045 owner-alias attribute of the parent alias, when delivering mail to a
6046 child alias that does not have its own owner alias. Then, local ad‐
6047 dresses from that child alias will be written to a new queue file, and
6048 a temporary error with one local address will not affect delivery to
6049 other mailing list members.
6050 Unfortunately, older Postfix releases reset the owner-alias attribute
6052 when delivering mail to a child alias that does not have its own owner
6053 alias. To be precise, this resets only the decision to create a new
6054 queue file, not the decision to override the envelope sender address.
6055 The local(8) delivery agent then attempts to deliver local addresses as
6056 soon as they come out of child alias expansion. If delivery to any ad‐
6057 dress from child alias expansion fails with a temporary error condi‐
6058 tion, the entire mailing list may be expanded repeatedly until the mail
6059 expires in the queue, resulting in multiple deliveries of the same mes‐
6060 sage to mailing list members.
6061
6063 Resolve a recipient address safely instead of correctly, by looking in‐
6064 side quotes.
6065 By default, the Postfix address resolver does not quote the address lo‐
6067 calpart as per RFC 822, so that additional @ or % or ! operators re‐
6068 main visible. This behavior is safe but it is also technically incor‐
6069 rect.
6070 If you specify "resolve_dequoted_address = no", then the Postfix re‐
6072 solver will not know about additional @ etc. operators in the address
6073 localpart. This opens opportunities for obscure mail relay attacks with
6074 user@domain@domain addresses when Postfix provides backup MX service
6075 for Sendmail systems.
6076
6078 Resolve an address that ends in the "@" null domain as if the local
6079 hostname were specified, instead of rejecting the address as invalid.
6080 This feature is available in Postfix 2.1 and later. Earlier versions
6082 always resolve the null domain as the local hostname.
6083 The Postfix SMTP server uses this feature to reject mail from or to ad‐
6085 dresses that end in the "@" null domain, and from addresses that re‐
6086 write into a form that ends in the "@" null domain.
6087
6089 Resolve "user@ipaddress" as "user@[ipaddress]", instead of rejecting
6090 the address as invalid.
6091 This feature is available in Postfix 2.3 and later.
6093
6095 Avoid logging that implies white is better than black. Instead use 'al‐
6096 lowlist', 'denylist', and variations of those words.
6097 This feature is available in Postfix 3.6 and later.
6099
6101 The name of the address rewriting service. This service rewrites ad‐
6102 dresses to standard form and resolves them to a (delivery method,
6103 next-hop host, recipient) triple.
6104 This feature is available in Postfix 2.0 and later.
6106
6108 The name of the directory with example Postfix configuration files.
6109 Starting with Postfix 2.1, these files have been replaced with the
6110 postconf(5) manual page.
6111
6113 When authenticating to a remote SMTP or LMTP server with the default
6114 setting "no", send no SASL authoriZation ID (authzid); send only the
6115 SASL authentiCation ID (authcid) plus the authcid's password.
6116 The non-default setting "yes" enables the behavior of older Postfix
6118 versions. These always send a SASL authzid that is equal to the SASL
6119 authcid, but this causes interoperability problems with some SMTP
6120 servers.
6121 This feature is available in Postfix 2.4.4 and later.
6123
6125 This parameter should not be used. It was replaced by sender_depen‐
6126 dent_relayhost_maps in Postfix version 2.3.
6127
6129 Optional BCC (blind carbon-copy) address lookup tables, indexed by
6130 sender address. The BCC address (multiple results are not supported)
6131 is added when mail enters from outside of Postfix.
6132 Specify zero or more "type:name" lookup tables, separated by whitespace
6134 or comma. Tables will be searched in the specified order until a match
6135 is found.
6136 The table search order is as follows:
6138 • Look up the "user+extension@domain.tld" address including the
6140 optional address extension.
6141 • Look up the "user@domain.tld" address without the optional ad‐
6143 dress extension.
6144 • Look up the "user+extension" address local part when the sender
6146 domain equals $myorigin, $mydestination, $inet_interfaces or
6147 $proxy_interfaces.
6148 • Look up the "user" address local part when the sender domain
6150 equals $myorigin, $mydestination, $inet_interfaces or $proxy_in‐
6151 terfaces.
6152 • Look up the "@domain.tld" part.
6154 Note: with Postfix 2.3 and later the BCC address is added as if it was
6156 specified with NOTIFY=NONE. The sender will not be notified when the
6157 BCC address is undeliverable, as long as all down-stream software im‐
6158 plements RFC 3461.
6159 Note: with Postfix 2.2 and earlier the sender will be notified when the
6161 BCC address is undeliverable.
6162 Note: automatic BCC recipients are produced only for new mail. To
6164 avoid mailer loops, automatic BCC recipients are not generated after
6165 Postfix forwards mail internally, or after Postfix generates mail it‐
6166 self.
6167 Example:
6169 sender_bcc_maps = hash:/etc/postfix/sender_bcc
6171 After a change, run "postmap /etc/postfix/sender_bcc".
6173 This feature is available in Postfix 2.1 and later.
6175
6177 What addresses are subject to sender_canonical_maps address mapping.
6178 By default, sender_canonical_maps address mapping is applied to enve‐
6179 lope sender addresses, and to header sender addresses.
6180 Specify one or more of: envelope_sender, header_sender
6182 This feature is available in Postfix 2.2 and later.
6184
6186 Optional address mapping lookup tables for envelope and header sender
6187 addresses. The table format and lookups are documented in canoni‐
6188 cal(5).
6189 Example: you want to rewrite the SENDER address "user@ugly.domain" to
6191 "user@pretty.domain", while still being able to send mail to the RECIP‐
6192 IENT address "user@ugly.domain".
6193 Note: $sender_canonical_maps is processed before $canonical_maps.
6195 Example:
6197 sender_canonical_maps = hash:/etc/postfix/sender_canonical
6199
6201 A sender-dependent override for the global default_transport parameter
6202 setting. The tables are searched by the envelope sender address and
6203 @domain. A lookup result of DUNNO terminates the search without over‐
6204 riding the global default_transport parameter setting. This informa‐
6205 tion is overruled with the transport(5) table.
6206 Specify zero or more "type:name" lookup tables, separated by whitespace
6208 or comma. Tables will be searched in the specified order until a match
6209 is found.
6210 Note: this overrides default_transport, not transport_maps, and there‐
6212 fore the expected syntax is that of default_transport, not the syntax
6213 of transport_maps. Specifically, this does not support the trans‐
6214 port_maps syntax for null transport, null nexthop, or null email ad‐
6215 dresses.
6216 For safety reasons, this feature does not allow $number substitutions
6218 in regular expression maps.
6219 This feature is available in Postfix 2.7 and later.
6221
6223 A sender-dependent override for the global relayhost parameter setting.
6224 The tables are searched by the envelope sender address and @domain. A
6225 lookup result of DUNNO terminates the search without overriding the
6226 global relayhost parameter setting (Postfix 2.6 and later). This infor‐
6227 mation is overruled with relay_transport, sender_dependent_de‐
6228 fault_transport_maps, default_transport and with the transport(5) ta‐
6229 ble.
6230 Specify zero or more "type:name" lookup tables, separated by whitespace
6232 or comma. Tables will be searched in the specified order until a match
6233 is found.
6234 For safety reasons, this feature does not allow $number substitutions
6236 in regular expression maps.
6237 This feature is available in Postfix 2.3 and later.
6239
6241 Controls how the Postfix sendmail command converts email message line
6242 endings from <CR><LF> into UNIX format (<LF>).
6243 always Always convert message lines ending in <CR><LF>. This setting is
6245 the default with Postfix 2.9 and later.
6246 strict Convert message lines ending in <CR><LF> only if the first input
6248 line ends in <CR><LF>. This setting is backwards-compatible with
6249 Postfix 2.8 and earlier.
6250 never Never convert message lines ending in <CR><LF>. This setting ex‐
6252 ists for completeness only.
6253 This feature is available in Postfix 2.9 and later.
6255
6257 A Sendmail compatibility feature that specifies the location of the
6258 Postfix sendmail(1) command. This command can be used to submit mail
6259 into the Postfix queue.
6260
6262 The master.cf service name of a Postfix daemon process. This can be
6263 used to distinguish the logging from different services that use the
6264 same program name.
6265 Example master.cf entries:
6267 # Distinguish inbound MTA logging from submission and smtps logging.
6269 smtp inet n - n - - smtpd
6270 submission inet n - n - - smtpd
6271 -o syslog_name=postfix/$service_name
6272 smtps inet n - n - - smtpd
6273 -o syslog_name=postfix/$service_name
6274 # Distinguish outbound MTA logging from inbound relay logging.
6276 smtp unix - - n - - smtp
6277 relay unix - - n - - smtp
6278 -o syslog_name=postfix/$service_name
6279
6281 How long the Postfix master(8) waits before forking a server that ap‐
6282 pears to be malfunctioning.
6283 Time units: s (seconds), m (minutes), h (hours), d (days), w (weeks).
6285 The default time unit is s (seconds).
6286
6288 The group ownership of set-gid Postfix commands and of group-writable
6289 Postfix directories. When this parameter value is changed you need to
6290 re-run "postfix set-permissions" (with Postfix version 2.0 and earlier:
6291 "/etc/postfix/post-install set-permissions".
6292
6294 The location of Postfix dynamically-linked libraries (libpostfix-*.so),
6295 and the default location of Postfix database plugins (postfix-*.so)
6296 that have a relative pathname in the dynamicmaps.cf file. The
6297 shlib_directory parameter defaults to "no" when Postfix dynami‐
6298 cally-linked libraries and database plugins are disabled at compile
6299 time, otherwise it typically defaults to /usr/lib/postfix or /usr/lo‐
6300 cal/lib/postfix.
6301 Notes:
6303 • The directory specified with shlib_directory should contain only
6305 Postfix-related files. Postfix dynamically-linked libraries and
6306 database plugins should not be installed in a "public" system
6307 directory such as /usr/lib or /usr/local/lib. Linking Postfix
6308 dynamically-linked library files or database plugins into
6309 non-Postfix programs is not supported. Postfix dynami‐
6310 cally-linked libraries and database plugins implement a Post‐
6311 fix-internal API that changes without maintaining compatibility.
6312 • You can change the shlib_directory value after Postfix is built.
6314 However, you may have to run ldconfig or equivalent to prevent
6315 Postfix programs from failing because the libpostfix-*.so files
6316 are not found. No ldconfig command is needed if you keep the
6317 libpostfix-*.so files in the compiled-in default $shlib_direc‐
6318 tory location.
6319 This feature is available in Postfix 3.0 and later.
6321
6323 Display the name of the recipient table in the "User unknown" re‐
6324 sponses. The extra detail makes troubleshooting easier but also re‐
6325 veals information that is nobody else's business.
6326 This feature is available in Postfix 2.0 and later.
6328
6330 The name of the showq(8) service. This service produces mail queue sta‐
6331 tus reports.
6332 This feature is available in Postfix 2.0 and later.
6334
6336 The address type ("ipv6", "ipv4" or "any") that the Postfix SMTP client
6337 will try first, when a destination has IPv6 and IPv4 addresses with
6338 equal MX preference. This feature has no effect unless the inet_proto‐
6339 cols setting enables both IPv4 and IPv6.
6340 Postfix SMTP client address preference has evolved. With Postfix 2.8
6342 the default is "ipv6"; earlier implementations are hard-coded to prefer
6343 IPv6 over IPv4.
6344 Notes for mail delivery between sites that have both IPv4 and IPv6 con‐
6346 nectivity:
6347 • The setting "smtp_address_preference = ipv6" is unsafe. It can
6349 fail to deliver mail when there is an outage that affects IPv6,
6350 while the destination is still reachable over IPv4.
6351 • The setting "smtp_address_preference = any" is safe. With this,
6353 mail will eventually be delivered even if there is an outage
6354 that affects IPv6 or IPv4, as long as it does not affect both.
6355 This feature is available in Postfix 2.8 and later.
6357
6359 In the context of email address verification, the SMTP protocol stage
6360 that determines whether an email address is deliverable. Specify one
6361 of "rcpt" or "data". The latter is needed with remote SMTP servers
6362 that reject recipients after the DATA command. Use transport_maps to
6363 apply this feature selectively:
6364 /etc/postfix/main.cf:
6366 transport_maps = hash:/etc/postfix/transport
6367 /etc/postfix/transport:
6369 smtp-domain-that-verifies-after-data smtp-data-target:
6370 lmtp-domain-that-verifies-after-data lmtp-data-target:
6371 /etc/postfix/master.cf:
6373 smtp-data-target unix - - n - - smtp
6374 -o smtp_address_verify_target=data
6375 lmtp-data-target unix - - n - - lmtp
6376 -o lmtp_address_verify_target=data
6377 Unselective use of the "data" target does no harm, but will result in
6379 unnecessary "lost connection after DATA" events at remote SMTP/LMTP
6380 servers.
6381 This feature is available in Postfix 3.0 and later.
6383
6385 Always send EHLO at the start of an SMTP session.
6386 With "smtp_always_send_ehlo = no", the Postfix SMTP client sends EHLO
6388 only when the word "ESMTP" appears in the server greeting banner (exam‐
6389 ple: 220 spike.porcupine.org ESMTP Postfix).
6390
6392 When a remote destination resolves to a combination of IPv4 and IPv6
6393 addresses, ensure that the Postfix SMTP client can try both address
6394 types before it runs into the smtp_mx_address_limit.
6395 This avoids an interoperability problem when a destination resolves to
6397 primarily IPv6 addresses, the smtp_address_limit feature eliminates
6398 most or all IPv4 addresses, and the destination is not reachable over
6399 IPv6.
6400 This feature is available in Postfix 3.3 and later.
6402
6404 An optional numerical network address that the Postfix SMTP client
6405 should bind to when making an IPv4 connection.
6406 This can be specified in the main.cf file for all SMTP clients, or it
6408 can be specified in the master.cf file for a specific client, for exam‐
6409 ple:
6410 /etc/postfix/master.cf:
6412 smtp ... smtp -o smtp_bind_address=11.22.33.44
6413 Note 1: when inet_interfaces specifies no more than one IPv4 address,
6415 and that address is a non-loopback address, it is automatically used as
6416 the smtp_bind_address. This supports virtual IP hosting, but can be a
6417 problem on multi-homed firewalls. See the inet_interfaces documentation
6418 for more detail.
6419 Note 2: address information may be enclosed inside [], but this form is
6421 not required here.
6422
6424 An optional numerical network address that the Postfix SMTP client
6425 should bind to when making an IPv6 connection.
6426 This feature is available in Postfix 2.2 and later.
6428 This can be specified in the main.cf file for all SMTP clients, or it
6430 can be specified in the master.cf file for a specific client, for exam‐
6431 ple:
6432 /etc/postfix/master.cf:
6434 smtp ... smtp -o smtp_bind_address6=1:2:3:4:5:6:7:8
6435 Note 1: when inet_interfaces specifies no more than one IPv6 address,
6437 and that address is a non-loopback address, it is automatically used as
6438 the smtp_bind_address6. This supports virtual IP hosting, but can be a
6439 problem on multi-homed firewalls. See the inet_interfaces documentation
6440 for more detail.
6441 Note 2: address information may be enclosed inside [], but this form is
6443 not recommended here.
6444
6446 Restricted body_checks(5) tables for the Postfix SMTP client. These
6447 tables are searched while mail is being delivered. Actions that change
6448 the delivery time or destination are not available.
6449 This feature is available in Postfix 2.5 and later.
6451
6453 When the remote SMTP servername is a DNS CNAME, replace the servername
6454 with the result from CNAME expansion for the purpose of logging, SASL
6455 password lookup, TLS policy decisions, or TLS certificate verification.
6456 The value "no" hardens Postfix smtp_tls_per_site hostname-based poli‐
6457 cies against false hostname information in DNS CNAME records, and makes
6458 SASL password file lookups more predictable. This is the default set‐
6459 ting as of Postfix 2.3.
6460 When DNS CNAME records are validated with secure DNS lookups
6462 (smtp_dns_support_level = dnssec), they are always allowed to override
6463 the above servername (Postfix 2.11 and later).
6464 This feature is available in Postfix 2.2.9 and later.
6466
6468 The Postfix SMTP client time limit for completing a TCP connection, or
6469 zero (use the operating system built-in time limit).
6470 When no connection can be made within the deadline, the Postfix SMTP
6472 client tries the next address on the mail exchanger list. Specify 0 to
6473 disable the time limit (i.e. use whatever timeout is implemented by the
6474 operating system).
6475 Time units: s (seconds), m (minutes), h (hours), d (days), w (weeks).
6477 The default time unit is s (seconds).
6478
6480 Permanently enable SMTP connection caching for the specified destina‐
6481 tions. With SMTP connection caching, a connection is not closed imme‐
6482 diately after completion of a mail transaction. Instead, the connec‐
6483 tion is kept open for up to $smtp_connection_cache_time_limit seconds.
6484 This allows connections to be reused for other deliveries, and can im‐
6485 prove mail delivery performance.
6486 Specify a comma or white space separated list of destinations or
6488 pseudo-destinations:
6489 • if mail is sent without a relay host: a domain name (the
6491 right-hand side of an email address, without the [] around a nu‐
6492 meric IP address),
6493 • if mail is sent via a relay host: a relay host name (without []
6495 or non-default TCP port), as specified in main.cf or in the
6496 transport map,
6497 • if mail is sent via a UNIX-domain socket: a pathname (without
6499 the unix: prefix),
6500 • a /file/name with domain names and/or relay host names as de‐
6502 fined above,
6503 • a "type:table" with domain names and/or relay host names on the
6505 left-hand side. The right-hand side result from "type:table"
6506 lookups is ignored.
6507 This feature is available in Postfix 2.2 and later.
6509
6511 Temporarily enable SMTP connection caching while a destination has a
6512 high volume of mail in the active queue. With SMTP connection caching,
6513 a connection is not closed immediately after completion of a mail
6514 transaction. Instead, the connection is kept open for up to $smtp_con‐
6515 nection_cache_time_limit seconds. This allows connections to be reused
6516 for other deliveries, and can improve mail delivery performance.
6517 This feature is available in Postfix 2.2 and later.
6519
6521 When SMTP connection caching is enabled, the amount of time that an un‐
6522 used SMTP client socket is kept open before it is closed. Do not spec‐
6523 ify larger values without permission from the remote sites.
6524 This feature is available in Postfix 2.2 and later.
6526
6528 When SMTP connection caching is enabled, the number of times that an
6529 SMTP session may be reused before it is closed, or zero (no limit).
6530 With a reuse count limit of N, a connection is used up to N+1 times.
6531 NOTE: This feature is unsafe. When a high-volume destination has multi‐
6533 ple inbound MTAs, then the slowest inbound MTA will attract the most
6534 connections to that destination. This limitation does not exist with
6535 the smtp_connection_reuse_time_limit feature.
6536 This feature is available in Postfix 2.11.
6538
6540 The amount of time during which Postfix will use an SMTP connection re‐
6541 peatedly. The timer starts when the connection is initiated (i.e. it
6542 includes the connect, greeting and helo latency, in addition to the la‐
6543 tencies of subsequent mail delivery transactions).
6544 This feature addresses a performance stability problem with remote SMTP
6546 servers. This problem is not specific to Postfix: it can happen when
6547 any MTA sends large amounts of SMTP email to a site that has multiple
6548 MX hosts.
6549 The problem starts when one of a set of MX hosts becomes slower than
6551 the rest. Even though SMTP clients connect to fast and slow MX hosts
6552 with equal probability, the slow MX host ends up with more simultaneous
6553 inbound connections than the faster MX hosts, because the slow MX host
6554 needs more time to serve each client request.
6555 The slow MX host becomes a connection attractor. If one MX host be‐
6557 comes N times slower than the rest, it dominates mail delivery latency
6558 unless there are more than N fast MX hosts to counter the effect. And
6559 if the number of MX hosts is smaller than N, the mail delivery latency
6560 becomes effectively that of the slowest MX host divided by the total
6561 number of MX hosts.
6562 The solution uses connection caching in a way that differs from Postfix
6564 version 2.2. By limiting the amount of time during which a connection
6565 can be used repeatedly (instead of limiting the number of deliveries
6566 over that connection), Postfix not only restores fairness in the dis‐
6567 tribution of simultaneous connections across a set of MX hosts, it also
6568 favors deliveries over connections that perform well, which is exactly
6569 what we want.
6570 The default reuse time limit, 300s, is comparable to the various smtp
6572 transaction timeouts which are fair estimates of maximum excess latency
6573 for a slow delivery. Note that hosts may accept thousands of messages
6574 over a single connection within the default connection reuse time
6575 limit. This number is much larger than the default Postfix version 2.2
6576 limit of 10 messages per cached connection. It may prove necessary to
6577 lower the limit to avoid interoperability issues with MTAs that exhibit
6578 bugs when many messages are delivered via a single connection. A lower
6579 reuse time limit risks losing the benefit of connection reuse when the
6580 average connection and mail delivery latency exceeds the reuse time
6581 limit.
6582 This feature is available in Postfix 2.3 and later.
6584
6586 The Postfix SMTP client time limit for sending the SMTP ".", and for
6587 receiving the remote SMTP server response.
6588 When no response is received within the deadline, a warning is logged
6590 that the mail may be delivered multiple times.
6591 Time units: s (seconds), m (minutes), h (hours), d (days), w (weeks).
6593 The default time unit is s (seconds).
6594
6596 The Postfix SMTP client time limit for sending the SMTP DATA command,
6597 and for receiving the remote SMTP server response.
6598 Time units: s (seconds), m (minutes), h (hours), d (days), w (weeks).
6600 The default time unit is s (seconds).
6601
6603 The Postfix SMTP client time limit for sending the SMTP message con‐
6604 tent. When the connection makes no progress for more than
6605 $smtp_data_xfer_timeout seconds the Postfix SMTP client terminates the
6606 transfer.
6607 Time units: s (seconds), m (minutes), h (hours), d (days), w (weeks).
6609 The default time unit is s (seconds).
6610
6612 Defer mail delivery when no MX record resolves to an IP address.
6613 The default (no) is to return the mail as undeliverable. With older
6615 Postfix versions the default was to keep trying to deliver the mail un‐
6616 til someone fixed the MX record or until the mail was too old.
6617 Note: the Postfix SMTP client always ignores MX records with equal or
6619 worse preference than the local MTA itself.
6620 This feature is available in Postfix 2.1 and later.
6622
6624 Optional filter for the smtp(8) delivery agent to change the delivery
6625 status code or explanatory text of successful or unsuccessful deliver‐
6626 ies. See default_delivery_status_filter for details.
6627 NOTE: This feature modifies Postfix SMTP client error or non-error mes‐
6629 sages that may or may not be derived from remote SMTP server responses.
6630 In contrast, the smtp_reply_filter feature modifies remote SMTP server
6631 responses only.
6632
6634 rency_limit)
6635 The maximal number of parallel deliveries to the same destination via
6636 the smtp message delivery transport. This limit is enforced by the
6637 queue manager. The message delivery transport name is the first field
6638 in the entry in the master.cf file.
6639
6641 ent_limit)
6642 The maximal number of recipients per message for the smtp message de‐
6643 livery transport. This limit is enforced by the queue manager. The mes‐
6644 sage delivery transport name is the first field in the entry in the
6645 master.cf file.
6646 Setting this parameter to a value of 1 changes the meaning of smtp_des‐
6648 tination_concurrency_limit from concurrency per domain into concurrency
6649 per recipient.
6650
6652 Lookup tables, indexed by the remote SMTP server address, with case in‐
6653 sensitive lists of EHLO keywords (pipelining, starttls, auth, etc.)
6654 that the Postfix SMTP client will ignore in the EHLO response from a
6655 remote SMTP server. See smtp_discard_ehlo_keywords for details. The ta‐
6656 ble is not indexed by hostname for consistency with smtpd_dis‐
6657 card_ehlo_keyword_address_maps.
6658 Specify zero or more "type:name" lookup tables, separated by whitespace
6660 or comma. Tables will be searched in the specified order until a match
6661 is found.
6662 This feature is available in Postfix 2.2 and later.
6664
6666 A case insensitive list of EHLO keywords (pipelining, starttls, auth,
6667 etc.) that the Postfix SMTP client will ignore in the EHLO response
6668 from a remote SMTP server.
6669 This feature is available in Postfix 2.2 and later.
6671 Notes:
6673 • Specify the silent-discard pseudo keyword to prevent this action
6675 from being logged.
6676 • Use the smtp_discard_ehlo_keyword_address_maps feature to dis‐
6678 card EHLO keywords selectively.
6679
6681 Optional filter for Postfix SMTP client DNS lookup results. Specify
6682 zero or more lookup tables. The lookup tables are searched in the
6683 given order for a match with the DNS lookup result, converted to the
6684 following form:
6685 name ttl class type preference value
6687 The class field is always "IN", the preference field exists only for MX
6689 records, the names of hosts, domains, etc. end in ".", and those names
6690 are in ASCII form (xn--mumble form in the case of UTF8 names).
6691 When a match is found, the table lookup result specifies an action. By
6693 default, the table query and the action name are case-insensitive.
6694 Currently, only the IGNORE action is implemented.
6695 Notes:
6697 • Postfix DNS reply filters have no effect on implicit DNS lookups
6699 through nsswitch.conf or equivalent mechanisms.
6700 • The Postfix SMTP/LMTP client uses smtp_dns_reply_filter and
6702 lmtp_dns_reply_filter only to discover a remote SMTP or LMTP
6703 service (record types MX, A, AAAA, and TLSA). These lookups are
6704 also made to implement the features reject_unverified_sender and
6705 reject_unverified_recipient.
6706 • The Postfix SMTP/LMTP client defers mail delivery when a filter
6708 removes all lookup results from a successful query.
6709 • Postfix SMTP server uses smtpd_dns_reply_filter only to look up
6711 MX, A, AAAA, and TXT records to implement the features re‐
6712 ject_unknown_helo_hostname, reject_unknown_sender_domain, re‐
6713 ject_unknown_recipient_domain, reject_rbl_*, and reject_rhsbl_*.
6714 • The Postfix SMTP server logs a warning or defers mail delivery
6716 when a filter removes all lookup results from a successful
6717 query.
6718 Example: ignore Google AAAA records in Postfix SMTP client DNS lookups,
6720 because Google sometimes hard-rejects mail from IPv6 clients with valid
6721 PTR etc. records.
6722 /etc/postfix/main.cf:
6724 smtp_dns_reply_filter = pcre:/etc/postfix/smtp_dns_reply_filter
6725 /etc/postfix/smtp_dns_reply_filter:
6727 # /domain ttl IN AAAA address/ action, all case-insensitive.
6728 # Note: the domain name ends in ".".
6729 /^\S+\.google\.com\.\s+\S+\s+\S+\s+AAAA\s+/ IGNORE
6730 This feature is available in Postfix 3.0 and later.
6732
6734 DNS Resolver options for the Postfix SMTP client. Specify zero or more
6735 of the following options, separated by comma or whitespace. Option
6736 names are case-sensitive. Some options refer to domain names that are
6737 specified in the file /etc/resolv.conf or equivalent.
6738 res_defnames
6740 Append the current domain name to single-component names (those
6741 that do not contain a "." character). This can produce incorrect
6742 results, and is the hard-coded behavior prior to Postfix 2.8.
6743 res_dnsrch
6745 Search for host names in the current domain and in parent do‐
6746 mains. This can produce incorrect results and is therefore not
6747 recommended.
6748 This feature is available in Postfix 2.8 and later.
6750
6752 Level of DNS support in the Postfix SMTP client. With "smtp_dns_sup‐
6753 port_level" left at its empty default value, the legacy "dis‐
6754 able_dns_lookups" parameter controls whether DNS is enabled in the
6755 Postfix SMTP client, otherwise the legacy parameter is ignored.
6756 Specify one of the following:
6758 disabled
6760 Disable DNS lookups. No MX lookups are performed and hostname
6761 to address lookups are unconditionally "native". This setting
6762 is not appropriate for hosts that deliver mail to the public In‐
6763 ternet. Some obsolete how-to documents recommend disabling DNS
6764 lookups in some configurations with content_filters. This is no
6765 longer required and strongly discouraged.
6766 enabled
6768 Enable DNS lookups. Nexthop destination domains not enclosed in
6769 "[]" will be subject to MX lookups. If "dns" and "native" are
6770 included in the "smtp_host_lookup" parameter value, DNS will be
6771 queried first to resolve MX-host A records, followed by "native"
6772 lookups if no answer is found in DNS.
6773 dnssec Enable DNSSEC lookups. The "dnssec" setting differs from the
6775 "enabled" setting above in the following ways:
6776 • Any MX lookups will set RES_USE_DNSSEC and RES_USE_EDNS0 to re‐
6778 quest DNSSEC-validated responses. If the MX response is
6779 DNSSEC-validated the corresponding hostnames are considered val‐
6780 idated.
6781 • The address lookups of validated hostnames are also validated,
6783 (provided of course "smtp_host_lookup" includes "dns", see be‐
6784 low).
6785 • Temporary failures in DNSSEC-enabled hostname-to-address resolu‐
6787 tion block any "native" lookups. Additional "native" lookups
6788 only happen when DNSSEC lookups hard-fail (NODATA or NXDOMAIN).
6789 The Postfix SMTP client considers non-MX "[nexthop]" and "[nex‐
6791 thop]:port" destinations equivalent to statically-validated MX records
6792 of the form "nexthop. IN MX 0 nexthop." Therefore, with "dnssec" sup‐
6793 port turned on, validated hostname-to-address lookups apply to the nex‐
6794 thop domain of any "[nexthop]" or "[nexthop]:port" destination. This
6795 is also true for LMTP "inet:host" and "inet:host:port" destinations, as
6796 LMTP hostnames are never subject to MX lookups.
6797 The "dnssec" setting is recommended only if you plan to use the dane or
6799 dane-only TLS security level, otherwise enabling DNSSEC support in
6800 Postfix offers no additional security. Postfix DNSSEC support relies
6801 on an upstream recursive nameserver that validates DNSSEC signatures.
6802 Such a DNS server will always filter out forged DNS responses, even
6803 when Postfix itself is not configured to use DNSSEC.
6804 When using Postfix DANE support the "smtp_host_lookup" parameter should
6806 include "dns", as DANE is not applicable to hosts resolved via "native"
6807 lookups.
6808 As mentioned above, Postfix is not a validating stub resolver; it re‐
6810 lies on the system's configured DNSSEC-validating recursive nameserver
6811 to perform all DNSSEC validation. Since this nameserver's DNSSEC-vali‐
6812 dated responses will be fully trusted, it is strongly recommended that
6813 the MTA host have a local DNSSEC-validating recursive caching name‐
6814 server listening on a loopback address, and be configured to use only
6815 this nameserver for all lookups. Otherwise, Postfix may remain subject
6816 to man-in-the-middle attacks that forge responses from the recursive
6817 nameserver
6818 DNSSEC support requires a version of Postfix compiled against a reason‐
6820 ably-modern DNS resolver(3) library that implements the RES_USE_DNSSEC
6821 and RES_USE_EDNS0 resolver options.
6822 This feature is available in Postfix 2.11 and later.
6824
6826 Enforcement mode: require that remote SMTP servers use TLS encryption,
6827 and never send mail in the clear. This also requires that the remote
6828 SMTP server hostname matches the information in the remote server cer‐
6829 tificate, and that the remote SMTP server certificate was issued by a
6830 CA that is trusted by the Postfix SMTP client. If the certificate
6831 doesn't verify or the hostname doesn't match, delivery is deferred and
6832 mail stays in the queue.
6833 The server hostname is matched against all names provided as dNSNames
6835 in the SubjectAlternativeName. If no dNSNames are specified, the Com‐
6836 monName is checked. The behavior may be changed with the smtp_tls_en‐
6837 force_peername option.
6838 This option is useful only if you are definitely sure that you will
6840 only connect to servers that support RFC 2487 _and_ that provide valid
6841 server certificates. Typical use is for clients that send all their
6842 email to a dedicated mailhub.
6843 This feature is available in Postfix 2.2 and later. With Postfix 2.3
6845 and later use smtp_tls_security_level instead.
6846
6848 Optional list of relay hosts for SMTP destinations that can't be found
6849 or that are unreachable. With Postfix 2.2 and earlier this parameter is
6850 called fallback_relay.
6851 By default, mail is returned to the sender when a destination is not
6853 found, and delivery is deferred when a destination is unreachable.
6854 With bulk email deliveries, it can be beneficial to run the fallback
6856 relay MTA on the same host, so that it can reuse the sender IP address.
6857 This speeds up deliveries that are delayed by IP-based reputation sys‐
6858 tems (greylist, etc.).
6859 The fallback relays must be SMTP destinations. Specify a domain, host,
6861 host:port, [host]:port, [address] or [address]:port; the form [host]
6862 turns off MX lookups. If you specify multiple SMTP destinations, Post‐
6863 fix will try them in the specified order.
6864 To prevent mailer loops between MX hosts and fall-back hosts, Postfix
6866 version 2.2 and later will not use the fallback relays for destinations
6867 that it is MX host for (assuming DNS lookup is turned on).
6868
6870 Optional lookup tables that perform address rewriting in the Postfix
6871 SMTP client, typically to transform a locally valid address into a
6872 globally valid address when sending mail across the Internet. This is
6873 needed when the local machine does not have its own Internet domain
6874 name, but uses something like localdomain.local instead.
6875 Specify zero or more "type:name" lookup tables, separated by whitespace
6877 or comma. Tables will be searched in the specified order until a match
6878 is found.
6879 The table format and lookups are documented in generic(5); examples are
6881 shown in the ADDRESS_REWRITING_README and STANDARD_CONFIGURATION_README
6882 documents.
6883 This feature is available in Postfix 2.2 and later.
6885
6887 Restricted header_checks(5) tables for the Postfix SMTP client. These
6888 tables are searched while mail is being delivered. Actions that change
6889 the delivery time or destination are not available.
6890 This feature is available in Postfix 2.5 and later.
6892
6894 The hostname to send in the SMTP HELO or EHLO command.
6895 The default value is the machine hostname. Specify a hostname or
6897 [ip.add.re.ss].
6898 This information can be specified in the main.cf file for all SMTP
6900 clients, or it can be specified in the master.cf file for a specific
6901 client, for example:
6902 /etc/postfix/master.cf:
6904 mysmtp ... smtp -o smtp_helo_name=foo.bar.com
6905 This feature is available in Postfix 2.0 and later.
6907
6909 The Postfix SMTP client time limit for sending the HELO or EHLO com‐
6910 mand, and for receiving the initial remote SMTP server response.
6911 Time units: s (seconds), m (minutes), h (hours), d (days), w (weeks).
6913 The default time unit is s (seconds).
6914
6916 What mechanisms the Postfix SMTP client uses to look up a host's IP ad‐
6917 dress. This parameter is ignored when DNS lookups are disabled (see:
6918 disable_dns_lookups and smtp_dns_support_level). The "dns" mechanism
6919 is always tried before "native" if both are listed.
6920 Specify one of the following:
6922 dns Hosts can be found in the DNS (preferred).
6924 native Use the native naming service only (nsswitch.conf, or equivalent
6926 mechanism).
6927 dns, native
6929 Use the native service for hosts not found in the DNS.
6930 This feature is available in Postfix 2.1 and later.
6932
6934 The maximal length of message header and body lines that Postfix will
6935 send via SMTP. This limit does not include the <CR><LF> at the end of
6936 each line. Longer lines are broken by inserting "<CR><LF><SPACE>", to
6937 minimize the damage to MIME formatted mail. Specify zero to disable
6938 this limit.
6939 The Postfix limit of 998 characters not including <CR><LF> is consis‐
6941 tent with the SMTP limit of 1000 characters including <CR><LF>. The
6942 Postfix limit was 990 with Postfix 2.8 and earlier.
6943
6945 The Postfix SMTP client time limit for sending the MAIL FROM command,
6946 and for receiving the remote SMTP server response.
6947 Time units: s (seconds), m (minutes), h (hours), d (days), w (weeks).
6949 The default time unit is s (seconds).
6950
6952 Restricted mime_header_checks(5) tables for the Postfix SMTP client.
6953 These tables are searched while mail is being delivered. Actions that
6954 change the delivery time or destination are not available.
6955 This feature is available in Postfix 2.5 and later.
6957
6959 The maximal number of MX (mail exchanger) IP addresses that can result
6960 from Postfix SMTP client mail exchanger lookups, or zero (no limit).
6961 Prior to Postfix version 2.3, this limit was disabled by default.
6962 This feature is available in Postfix 2.1 and later.
6964
6966 The maximal number of SMTP sessions per delivery request before the
6967 Postfix SMTP client gives up or delivers to a fall-back relay host, or
6968 zero (no limit). This restriction ignores sessions that fail to com‐
6969 plete the SMTP initial handshake (Postfix version 2.2 and earlier) or
6970 that fail to complete the EHLO and TLS handshake (Postfix version 2.3
6971 and later).
6972 This feature is available in Postfix 2.1 and later.
6974
6976 Restricted nested_header_checks(5) tables for the Postfix SMTP client.
6977 These tables are searched while mail is being delivered. Actions that
6978 change the delivery time or destination are not available.
6979 This feature is available in Postfix 2.5 and later.
6981
6983 Never send EHLO at the start of an SMTP session. See also the smtp_al‐
6984 ways_send_ehlo parameter.
6985
6987 Change the behavior of the smtp_*_timeout time limits, from a time
6988 limit per read or write system call, to a time limit to send or receive
6989 a complete record (an SMTP command line, SMTP response line, SMTP mes‐
6990 sage content line, or TLS protocol message). This limits the impact
6991 from hostile peers that trickle data one byte at a time.
6992 Note: when per-record deadlines are enabled, a short timeout may cause
6994 problems with TLS over very slow network connections. The reasons are
6995 that a TLS protocol message can be up to 16 kbytes long (with TLSv1),
6996 and that an entire TLS protocol message must be sent or received within
6997 the per-record deadline.
6998 This feature is available in Postfix 2.9 and later. With older Postfix
7000 releases, the behavior is as if this parameter is set to "no".
7001
7003 How long the Postfix SMTP client pauses before sending ".<CR><LF>" in
7004 order to work around the PIX firewall "<CR><LF>.<CR><LF>" bug.
7005 Choosing a too short time makes this workaround ineffective when send‐
7007 ing large messages over slow network connections.
7008
7010 Lookup tables, indexed by the remote SMTP server address, with per-des‐
7011 tination workarounds for CISCO PIX firewall bugs. The table is not in‐
7012 dexed by hostname for consistency with smtp_discard_ehlo_keyword_ad‐
7013 dress_maps.
7014 Specify zero or more "type:name" lookup tables, separated by whitespace
7016 or comma. Tables will be searched in the specified order until a match
7017 is found.
7018 This feature is available in Postfix 2.4 and later.
7020
7022 How long a message must be queued before the Postfix SMTP client turns
7023 on the PIX firewall "<CR><LF>.<CR><LF>" bug workaround for delivery
7024 through firewalls with "smtp fixup" mode turned on.
7025 By default, the workaround is turned off for mail that is queued for
7027 less than 500 seconds. In other words, the workaround is normally
7028 turned off for the first delivery attempt.
7029 Specify 0 to enable the PIX firewall "<CR><LF>.<CR><LF>" bug workaround
7031 upon the first delivery attempt.
7032
7034 A list that specifies zero or more workarounds for CISCO PIX firewall
7035 bugs. These workarounds are implemented by the Postfix SMTP client.
7036 Workaround names are separated by comma or space, and are case insensi‐
7037 tive. This parameter setting can be overruled with per-destination
7038 smtp_pix_workaround_maps settings.
7039 delay_dotcrlf
7041 Insert a delay before sending ".<CR><LF>" after the end of the
7042 message content. The delay is subject to the smtp_pix_work‐
7043 around_delay_time and smtp_pix_workaround_threshold_time parame‐
7044 ter settings.
7045 disable_esmtp
7047 Disable all extended SMTP commands: send HELO instead of EHLO.
7048 This feature is available in Postfix 2.4 and later. The default set‐
7050 tings are backwards compatible with earlier Postfix versions.
7051
7053 The Postfix SMTP client time limit for sending the QUIT command, and
7054 for receiving the remote SMTP server response.
7055 Time units: s (seconds), m (minutes), h (hours), d (days), w (weeks).
7057 The default time unit is s (seconds).
7058
7060 Quote addresses in Postfix SMTP client MAIL FROM and RCPT TO commands
7061 as required by RFC 5321. This includes putting quotes around an address
7062 localpart that ends in ".".
7063 The default is to comply with RFC 5321. If you have to send mail to a
7065 broken SMTP server, configure a special SMTP client in master.cf:
7066 /etc/postfix/master.cf:
7068 broken-smtp . . . smtp -o smtp_quote_rfc821_envelope=no
7069 and route mail for the destination in question to the "broken-smtp"
7071 message delivery with a transport(5) table.
7072 This feature is available in Postfix 2.1 and later.
7074
7076 Randomize the order of equal-preference MX host addresses. This is a
7077 performance feature of the Postfix SMTP client.
7078
7080 The Postfix SMTP client time limit for sending the SMTP RCPT TO com‐
7081 mand, and for receiving the remote SMTP server response.
7082 Time units: s (seconds), m (minutes), h (hours), d (days), w (weeks).
7084 The default time unit is s (seconds).
7085
7087 A mechanism to transform replies from remote SMTP servers one line at a
7088 time. This is a last-resort tool to work around server replies that
7089 break interoperability with the Postfix SMTP client. Other uses in‐
7090 volve fault injection to test Postfix's handling of invalid responses.
7091 Notes:
7093 • In the case of a multi-line reply, the Postfix SMTP client uses
7095 the final reply line's numerical SMTP reply code and enhanced
7096 status code.
7097 • The numerical SMTP reply code (XYZ) takes precedence over the
7099 enhanced status code (X.Y.Z). When the enhanced status code
7100 initial digit differs from the SMTP reply code initial digit, or
7101 when no enhanced status code is present, the Postfix SMTP client
7102 uses a generic enhanced status code (X.0.0) instead.
7103 Specify the name of a "type:table" lookup table. The search string is a
7105 single SMTP reply line as received from the remote SMTP server, except
7106 that the trailing <CR><LF> are removed. When the lookup succeeds, the
7107 result replaces the single SMTP reply line.
7108 Examples:
7110 /etc/postfix/main.cf:
7112 smtp_reply_filter = pcre:/etc/postfix/reply_filter
7113 /etc/postfix/reply_filter:
7115 # Transform garbage into "250-filler..." so that it looks like
7116 # one line from a multi-line reply. It does not matter what we
7117 # substitute here as long it has the right syntax. The Postfix
7118 # SMTP client will use the final line's numerical SMTP reply
7119 # code and enhanced status code.
7120 !/^([2-5][0-9][0-9]($|[- ]))/ 250-filler for garbage
7121 This feature is available in Postfix 2.7.
7123
7125 The Postfix SMTP client time limit for sending the RSET command, and
7126 for receiving the remote SMTP server response. The SMTP client sends
7127 RSET in order to finish a recipient address probe, or to verify that a
7128 cached session is still usable.
7129 This feature is available in Postfix 2.1 and later.
7131
7133 An optional table to prevent repeated SASL authentication failures with
7134 the same remote SMTP server hostname, username and password. Each table
7135 (key, value) pair contains a server name, a username and password, and
7136 the full server response. This information is stored when a remote SMTP
7137 server rejects an authentication attempt with a 535 reply code. As
7138 long as the smtp_sasl_password_maps information does no change, and as
7139 long as the smtp_sasl_auth_cache_name information does not expire (see
7140 smtp_sasl_auth_cache_time) the Postfix SMTP client avoids SASL authen‐
7141 tication attempts with the same server, username and password, and in‐
7142 stead bounces or defers mail as controlled with the
7143 smtp_sasl_auth_soft_bounce configuration parameter.
7144 Use a per-destination delivery concurrency of 1 (for example,
7146 "smtp_destination_concurrency_limit = 1", "relay_destination_concur‐
7147 rency_limit = 1", etc.), otherwise multiple delivery agents may experi‐
7148 ence a login failure at the same time.
7149 The table must be accessed via the proxywrite service, i.e. the map
7151 name must start with "proxy:". The table should be stored under the di‐
7152 rectory specified with the data_directory parameter.
7153 This feature uses cryptographic hashing to protect plain-text pass‐
7155 words, and requires that Postfix is compiled with TLS support.
7156 Example:
7158 smtp_sasl_auth_cache_name = proxy:btree:/var/lib/postfix/sasl_auth_cache
7160 This feature is available in Postfix 2.5 and later.
7162
7164 The maximal age of an smtp_sasl_auth_cache_name entry before it is re‐
7165 moved.
7166 This feature is available in Postfix 2.5 and later.
7168
7170 Enable SASL authentication in the Postfix SMTP client. By default, the
7171 Postfix SMTP client uses no authentication.
7172 Example:
7174 smtp_sasl_auth_enable = yes
7176
7178 When a remote SMTP server rejects a SASL authentication request with a
7179 535 reply code, defer mail delivery instead of returning mail as unde‐
7180 liverable. The latter behavior was hard-coded prior to Postfix version
7181 2.5.
7182 Note: the setting "yes" overrides the global soft_bounce parameter, but
7184 the setting "no" does not.
7185 Example:
7187 # Default as of Postfix 2.5
7189 smtp_sasl_auth_soft_bounce = yes
7190 # The old hard-coded default
7191 smtp_sasl_auth_soft_bounce = no
7192 This feature is available in Postfix 2.5 and later.
7194
7196 If non-empty, a Postfix SMTP client filter for the remote SMTP server's
7197 list of offered SASL mechanisms. Different client and server implemen‐
7198 tations may support different mechanism lists; by default, the Postfix
7199 SMTP client will use the intersection of the two. smtp_sasl_mecha‐
7200 nism_filter specifies an optional third mechanism list to intersect
7201 with.
7202 Specify mechanism names, "/file/name" patterns or "type:table" lookup
7204 tables. The right-hand side result from "type:table" lookups is ig‐
7205 nored. Specify "!pattern" to exclude a mechanism name from the list.
7206 The form "!/file/name" is supported only in Postfix version 2.4 and
7207 later.
7208 This feature is available in Postfix 2.2 and later.
7210 Examples:
7212 smtp_sasl_mechanism_filter = plain, login
7214 smtp_sasl_mechanism_filter = /etc/postfix/smtp_mechs
7215 smtp_sasl_mechanism_filter = !gssapi, !login, static:rest
7216
7218 Optional Postfix SMTP client lookup tables with one username:password
7219 entry per sender, remote hostname or next-hop domain. Per-sender lookup
7220 is done only when sender-dependent authentication is enabled. If no
7221 username:password entry is found, then the Postfix SMTP client will not
7222 attempt to authenticate to the remote host.
7223 The Postfix SMTP client opens the lookup table before going to chroot
7225 jail, so you can leave the password file in /etc/postfix.
7226 Specify zero or more "type:name" lookup tables, separated by whitespace
7228 or comma. Tables will be searched in the specified order until a match
7229 is found.
7230
7232 Implementation-specific information that the Postfix SMTP client passes
7233 through to the SASL plug-in implementation that is selected with
7234 smtp_sasl_type. Typically this specifies the name of a configuration
7235 file or rendezvous point.
7236 This feature is available in Postfix 2.3 and later.
7238
7240 Postfix SMTP client SASL security options; as of Postfix 2.3 the list
7241 of available features depends on the SASL client implementation that is
7242 selected with smtp_sasl_type.
7243 The following security features are defined for the cyrus client SASL
7245 implementation:
7246 Specify zero or more of the following:
7248 noplaintext
7250 Disallow methods that use plaintext passwords.
7251 noactive
7253 Disallow methods subject to active (non-dictionary) attack.
7254 nodictionary
7256 Disallow methods subject to passive (dictionary) attack.
7257 noanonymous
7259 Disallow methods that allow anonymous authentication.
7260 mutual_auth
7262 Only allow methods that provide mutual authentication (not
7263 available with SASL version 1).
7264 Example:
7266 smtp_sasl_security_options = noplaintext
7268
7270 The SASL authentication security options that the Postfix SMTP client
7271 uses for TLS encrypted SMTP sessions.
7272 This feature is available in Postfix 2.2 and later.
7274
7276 tions)
7277 The SASL authentication security options that the Postfix SMTP client
7278 uses for TLS encrypted SMTP sessions with a verified server certifi‐
7279 cate.
7280 When mail is sent to the public MX host for the recipient's domain,
7282 server certificates are by default optional, and delivery proceeds even
7283 if certificate verification fails. For delivery via a submission ser‐
7284 vice that requires SASL authentication, it may be appropriate to send
7285 plaintext passwords only when the connection to the server is strongly
7286 encrypted and the server identity is verified.
7287 The smtp_sasl_tls_verified_security_options parameter makes it possible
7289 to only enable plaintext mechanisms when a secure connection to the
7290 server is available. Submission servers subject to this policy must ei‐
7291 ther have verifiable certificates or offer suitable non-plaintext SASL
7292 mechanisms.
7293 This feature is available in Postfix 2.6 and later.
7295
7297 The SASL plug-in type that the Postfix SMTP client should use for au‐
7298 thentication. The available types are listed with the "postconf -A"
7299 command.
7300 This feature is available in Postfix 2.3 and later.
7302
7304 Whether or not to append the "AUTH=<>" option to the MAIL FROM command
7305 in SASL-authenticated SMTP sessions. The default is not to send this,
7306 to avoid problems with broken remote SMTP servers. Before Postfix 2.9
7307 the behavior is as if "smtp_send_dummy_mail_auth = yes".
7308 This feature is available in Postfix 2.9 and later.
7310
7312 Send the non-standard XFORWARD command when the Postfix SMTP server
7313 EHLO response announces XFORWARD support.
7314 This allows a Postfix SMTP delivery agent, used for injecting mail into
7316 a content filter, to forward the name, address, protocol and HELO name
7317 of the original client to the content filter and downstream queuing
7318 SMTP server. This can produce more useful logging than local‐
7319 host[127.0.0.1] etc.
7320 This feature is available in Postfix 2.1 and later.
7322
7324 Enable sender-dependent authentication in the Postfix SMTP client; this
7325 is available only with SASL authentication, and disables SMTP connec‐
7326 tion caching to ensure that mail from different senders will use the
7327 appropriate credentials.
7328 This feature is available in Postfix 2.3 and later.
7330
7332 Skip SMTP servers that greet with a 4XX status code (go away, try again
7333 later).
7334 By default, the Postfix SMTP client moves on the next mail exchanger.
7336 Specify "smtp_skip_4xx_greeting = no" if Postfix should defer delivery
7337 immediately.
7338 This feature is available in Postfix 2.0 and earlier. Later Postfix
7340 versions always skip remote SMTP servers that greet with a 4XX status
7341 code.
7342
7344 Skip remote SMTP servers that greet with a 5XX status code.
7345 By default, the Postfix SMTP client moves on the next mail exchanger.
7347 Specify "smtp_skip_5xx_greeting = no" if Postfix should bounce the mail
7348 immediately. Caution: the latter behavior appears to contradict RFC
7349 2821.
7350
7352 Do not wait for the response to the SMTP QUIT command.
7353
7355 Time limit for Postfix SMTP client write and read operations during TLS
7356 startup and shutdown handshake procedures.
7357 This feature is available in Postfix 2.2 and later.
7359
7361 The default TCP port that the Postfix SMTP client connects to. Specify
7362 a symbolic name (see services(5)) or a numeric port.
7363
7365 A file containing CA certificates of root CAs trusted to sign either
7366 remote SMTP server certificates or intermediate CA certificates. These
7367 are loaded into memory before the smtp(8) client enters the chroot
7368 jail. If the number of trusted roots is large, consider using
7369 smtp_tls_CApath instead, but note that the latter directory must be
7370 present in the chroot jail if the smtp(8) client is chrooted. This file
7371 may also be used to augment the client certificate trust chain, but it
7372 is best to include all the required certificates directly in
7373 $smtp_tls_cert_file (or, Postfix >= 3.4 $smtp_tls_chain_files).
7374 Specify "smtp_tls_CAfile = /path/to/system_CA_file" to use ONLY the
7376 system-supplied default Certification Authority certificates.
7377 Specify "tls_append_default_CA = no" to prevent Postfix from appending
7379 the system-supplied default CAs and trusting third-party certificates.
7380 Example:
7382 smtp_tls_CAfile = /etc/postfix/CAcert.pem
7384 This feature is available in Postfix 2.2 and later.
7386
7388 Directory with PEM format Certification Authority certificates that the
7389 Postfix SMTP client uses to verify a remote SMTP server certificate.
7390 Don't forget to create the necessary "hash" links with, for example,
7391 "$OPENSSL_HOME/bin/c_rehash /etc/postfix/certs".
7392 To use this option in chroot mode, this directory (or a copy) must be
7394 inside the chroot jail.
7395 Specify "smtp_tls_CApath = /path/to/system_CA_directory" to use ONLY
7397 the system-supplied default Certification Authority certificates.
7398 Specify "tls_append_default_CA = no" to prevent Postfix from appending
7400 the system-supplied default CAs and trusting third-party certificates.
7401 Example:
7403 smtp_tls_CApath = /etc/postfix/certs
7405 This feature is available in Postfix 2.2 and later.
7407
7409 Try to detect a mail hijacking attack based on a TLS protocol vulnera‐
7410 bility (CVE-2009-3555), where an attacker prepends malicious HELO,
7411 MAIL, RCPT, DATA commands to a Postfix SMTP client TLS session. The
7412 attack would succeed with non-Postfix SMTP servers that reply to the
7413 malicious HELO, MAIL, RCPT, DATA commands after negotiating the Postfix
7414 SMTP client TLS session.
7415 This feature is available in Postfix 2.7.
7417
7419 File with the Postfix SMTP client RSA certificate in PEM format. This
7420 file may also contain the Postfix SMTP client private RSA key, and
7421 these may be the same as the Postfix SMTP server RSA certificate and
7422 key file. With Postfix >= 3.4 the preferred way to configure client
7423 keys and certificates is via the "smtp_tls_chain_files" parameter.
7424 Do not configure client certificates unless you must present client TLS
7426 certificates to one or more servers. Client certificates are not usu‐
7427 ally needed, and can cause problems in configurations that work well
7428 without them. The recommended setting is to let the defaults stand:
7429 smtp_tls_cert_file =
7431 smtp_tls_key_file =
7432 smtp_tls_eccert_file =
7433 smtp_tls_eckey_file =
7434 # Obsolete DSA parameters
7435 smtp_tls_dcert_file =
7436 smtp_tls_dkey_file =
7437 # Postfix >= 3.4 interface
7438 smtp_tls_chain_files =
7439 The best way to use the default settings is to comment out the above
7441 parameters in main.cf if present.
7442 To enable remote SMTP servers to verify the Postfix SMTP client cer‐
7444 tificate, the issuing CA certificates must be made available to the
7445 server. You should include the required certificates in the client cer‐
7446 tificate file, the client certificate first, then the issuing CA(s)
7447 (bottom-up order).
7448 Example: the certificate for "client.example.com" was issued by "inter‐
7450 mediate CA" which itself has a certificate issued by "root CA". As the
7451 "root" super-user create the client.pem file with:
7452 # umask 077
7454 # cat client_key.pem client_cert.pem intermediate_CA.pem > chain.pem
7455 If you also want to verify remote SMTP server certificates issued by
7457 these CAs, you can add the CA certificates to the smtp_tls_CAfile, in
7458 which case it is not necessary to have them in the smtp_tls_cert_file,
7459 smtp_tls_dcert_file (obsolete) or smtp_tls_eccert_file.
7460 A certificate supplied here must be usable as an SSL client certificate
7462 and hence pass the "openssl verify -purpose sslclient ..." test.
7463 Example:
7465 smtp_tls_cert_file = /etc/postfix/chain.pem
7467 This feature is available in Postfix 2.2 and later.
7469
7471 List of one or more PEM files, each holding one or more private keys
7472 directly followed by a corresponding certificate chain. The file names
7473 are separated by commas and/or whitespace. This parameter obsoletes
7474 the legacy algorithm-specific key and certificate file settings. When
7475 this parameter is non-empty, the legacy parameters are ignored, and a
7476 warning is logged if any are also non-empty.
7477 With the proliferation of multiple private key algorithms-which, as of
7479 OpenSSL 1.1.1, include DSA (obsolete), RSA, ECDSA, Ed25519 and Ed448-it
7480 is increasingly impractical to use separate parameters to configure the
7481 key and certificate chain for each algorithm. Therefore, Postfix now
7482 supports storing multiple keys and corresponding certificate chains in
7483 a single file or in a set of files.
7484 Each key must appear immediately before the corresponding certificate,
7486 optionally followed by additional issuer certificates that complete the
7487 certificate chain for that key. When multiple files are specified,
7488 they are equivalent to a single file that is concatenated from those
7489 files in the given order. Thus, while a key must always precede its
7490 certificate and issuer chain, it can be in a separate file, so long as
7491 that file is listed immediately before the file that holds the corre‐
7492 sponding certificate chain. Once all the files are concatenated, the
7493 sequence of PEM objects must be: key1, cert1, [chain1], key2, cert2,
7494 [chain2], ..., keyN, certN, [chainN].
7495 Storing the private key in the same file as the corresponding certifi‐
7497 cate is more reliable. With the key and certificate in separate files,
7498 there is a chance that during key rollover a Postfix process might load
7499 a private key and certificate from separate files that don't match.
7500 Various operational errors may even result in a persistent broken con‐
7501 figuration in which the certificate does not match the private key.
7502 The file or files must contain at most one key of each type. If, for
7504 example, two or more RSA keys and corresponding chains are listed, de‐
7505 pending on the version of OpenSSL either only the last one will be used
7506 or an configuration error may be detected. Note that while "Ed25519"
7507 and "Ed448" are considered separate algorithms, the various ECDSA
7508 curves (typically one of prime256v1, secp384r1 or secp521r1) are con‐
7509 sidered as different parameters of a single "ECDSA" algorithm, so it is
7510 not presently possible to configure keys for more than one ECDSA curve.
7511 Example (separate files for each key and corresponding certificate
7513 chain):
7514 /etc/postfix/main.cf:
7516 smtp_tls_chain_files =
7517 ${config_directory}/ed25519.pem,
7518 ${config_directory}/ed448.pem,
7519 ${config_directory}/rsa.pem
7520 /etc/postfix/ed25519.pem:
7522 -----BEGIN PRIVATE KEY-----
7523 MC4CAQAwBQYDK2VwBCIEIEJfbbO4BgBQGBg9NAbIJaDBqZb4bC4cOkjtAH+Efbz3
7524 -----END PRIVATE KEY-----
7525 -----BEGIN CERTIFICATE-----
7526 MIIBKzCB3qADAgECAhQaw+rflRreYuUZBp0HuNn/e5rMZDAFBgMrZXAwFDESMBAG
7527 ...
7528 nC0egv51YPDWxEHom4QA
7529 -----END CERTIFICATE-----
7530 /etc/postfix/ed448.pem:
7532 -----BEGIN PRIVATE KEY-----
7533 MEcCAQAwBQYDK2VxBDsEOQf+m0P+G0qi+NZ0RolyeiE5zdlPQR8h8y4jByBifpIe
7534 LNler7nzHQJ1SLcOiXFHXlxp/84VZuh32A==
7535 -----END PRIVATE KEY-----
7536 -----BEGIN CERTIFICATE-----
7537 MIIBdjCB96ADAgECAhQSv4oP972KypOZPNPF4fmsiQoRHzAFBgMrZXEwFDESMBAG
7538 ...
7539 pQcWsx+4J29e6YWH3Cy/CdUaexKP4RPCZDrPX7bk5C2BQ+eeYOxyThMA
7540 -----END CERTIFICATE-----
7541 /etc/postfix/rsa.pem:
7543 -----BEGIN PRIVATE KEY-----
7544 MIIEvQIBADANBgkqhkiG9w0BAQEFAASCBKcwggSjAgEAAoIBAQDc4QusgkahH9rL
7545 ...
7546 ahQkZ3+krcaJvDSMgvu0tDc=
7547 -----END PRIVATE KEY-----
7548 -----BEGIN CERTIFICATE-----
7549 MIIC+DCCAeCgAwIBAgIUIUkrbk1GAemPCT8i9wKsTGDH7HswDQYJKoZIhvcNAQEL
7550 ...
7551 Rirz15HGVNTK8wzFd+nulPzwUo6dH2IU8KazmyRi7OGvpyrMlm15TRE2oyE=
7552 -----END CERTIFICATE-----
7553 Example (all keys and certificates in a single file):
7555 /etc/postfix/main.cf:
7557 smtp_tls_chain_files = ${config_directory}/chains.pem
7558 /etc/postfix/chains.pem:
7560 -----BEGIN PRIVATE KEY-----
7561 MC4CAQAwBQYDK2VwBCIEIEJfbbO4BgBQGBg9NAbIJaDBqZb4bC4cOkjtAH+Efbz3
7562 -----END PRIVATE KEY-----
7563 -----BEGIN CERTIFICATE-----
7564 MIIBKzCB3qADAgECAhQaw+rflRreYuUZBp0HuNn/e5rMZDAFBgMrZXAwFDESMBAG
7565 ...
7566 nC0egv51YPDWxEHom4QA
7567 -----END CERTIFICATE-----
7568 -----BEGIN PRIVATE KEY-----
7569 MEcCAQAwBQYDK2VxBDsEOQf+m0P+G0qi+NZ0RolyeiE5zdlPQR8h8y4jByBifpIe
7570 LNler7nzHQJ1SLcOiXFHXlxp/84VZuh32A==
7571 -----END PRIVATE KEY-----
7572 -----BEGIN CERTIFICATE-----
7573 MIIBdjCB96ADAgECAhQSv4oP972KypOZPNPF4fmsiQoRHzAFBgMrZXEwFDESMBAG
7574 ...
7575 pQcWsx+4J29e6YWH3Cy/CdUaexKP4RPCZDrPX7bk5C2BQ+eeYOxyThMA
7576 -----END CERTIFICATE-----
7577 -----BEGIN PRIVATE KEY-----
7578 MIIEvQIBADANBgkqhkiG9w0BAQEFAASCBKcwggSjAgEAAoIBAQDc4QusgkahH9rL
7579 ...
7580 ahQkZ3+krcaJvDSMgvu0tDc=
7581 -----END PRIVATE KEY-----
7582 -----BEGIN CERTIFICATE-----
7583 MIIC+DCCAeCgAwIBAgIUIUkrbk1GAemPCT8i9wKsTGDH7HswDQYJKoZIhvcNAQEL
7584 ...
7585 Rirz15HGVNTK8wzFd+nulPzwUo6dH2IU8KazmyRi7OGvpyrMlm15TRE2oyE=
7586 -----END CERTIFICATE-----
7587 This feature is available in Postfix 3.4 and later.
7589
7591 Obsolete Postfix < 2.3 control for the Postfix SMTP client TLS cipher
7592 list. As this feature applies to all TLS security levels, it is easy to
7593 create interoperability problems by choosing a non-default cipher list.
7594 Do not use a non-default TLS cipher list on hosts that deliver email to
7595 the public Internet: you will be unable to send email to servers that
7596 only support the ciphers you exclude. Using a restricted cipher list
7597 may be more appropriate for an internal MTA, where one can exert some
7598 control over the TLS software and settings of the peer servers.
7599 Note: do not use "" quotes around the parameter value.
7601 This feature is available in Postfix version 2.2. It is not used with
7603 Postfix 2.3 and later; use smtp_tls_mandatory_ciphers instead.
7604
7606 The minimum TLS cipher grade that the Postfix SMTP client will use with
7607 opportunistic TLS encryption. Cipher types listed in smtp_tls_ex‐
7608 clude_ciphers are excluded from the base definition of the selected ci‐
7609 pher grade. The default value is "medium" for Postfix releases after
7610 the middle of 2015, "export" for older releases.
7611 When TLS is mandatory the cipher grade is chosen via the
7613 smtp_tls_mandatory_ciphers configuration parameter, see there for syn‐
7614 tax details. See smtp_tls_policy_maps for information on how to config‐
7615 ure ciphers on a per-destination basis.
7616 This feature is available in Postfix 2.6 and later. With earlier Post‐
7618 fix releases only the smtp_tls_mandatory_ciphers parameter is imple‐
7619 mented, and opportunistic TLS always uses "export" or better (i.e. all)
7620 ciphers.
7621
7623 Try to make multiple deliveries per TLS-encrypted connection. This
7624 uses the tlsproxy(8) service to encrypt an SMTP connection, uses the
7625 scache(8) service to save that connection, and relies on hints from the
7626 qmgr(8) daemon.
7627 See "Client-side TLS connection reuse" for background details.
7629 This feature is available in Postfix 3.4 and later.
7631
7633 The TLS policy for MX hosts with "secure" TLSA records when the nexthop
7634 destination security level is dane, but the MX record was found via an
7635 "insecure" MX lookup. The choices are:
7636 may The TLSA records will be ignored and TLS will be optional. If
7638 the MX host does not appear to support STARTTLS, or the STARTTLS
7639 handshake fails, mail may be sent in the clear.
7640 encrypt
7642 The TLSA records will signal a requirement to use TLS. While
7643 TLS encryption will be required, authentication will not be per‐
7644 formed.
7645 dane The TLSA records will be used just as with "secure" MX records.
7647 TLS encryption will be required, and, if at least one of the
7648 TLSA records is "usable", authentication will be required. When
7649 authentication succeeds, it will be logged only as "Trusted",
7650 not "Verified", because the MX host name could have been forged.
7651 The default setting for Postfix >= 3.6 is "dane" with
7652 "smtp_tls_security_level = dane", otherwise "may". This behavior
7653 was backported to Postfix versions 3.5.9, 3.4.19, 3.3.16.
7654 3.2.21. With earlier Postfix versions the default setting was
7655 always "dane".
7656 Though with "insecure" MX records an active attacker can compromise
7658 SMTP transport security by returning forged MX records, such attacks
7659 are "tamper-evident" since any forged MX hostnames will be recorded in
7660 the mail logs. Attackers who place a high value staying hidden may be
7661 deterred from forging MX records.
7662 This feature is available in Postfix 3.1 and later. The may policy is
7664 backwards-compatible with earlier Postfix versions.
7665
7667 File with the Postfix SMTP client DSA certificate in PEM format. This
7668 file may also contain the Postfix SMTP client private DSA key. The DSA
7669 algorithm is obsolete and should not be used.
7670 See the discussion under smtp_tls_cert_file for more details.
7672 Example:
7674 smtp_tls_dcert_file = /etc/postfix/client-dsa.pem
7676 This feature is available in Postfix 2.2 and later.
7678
7680 File with the Postfix SMTP client DSA private key in PEM format. This
7681 file may be combined with the Postfix SMTP client DSA certificate file
7682 specified with $smtp_tls_dcert_file. The DSA algorithm is obsolete and
7683 should not be used.
7684 The private key must be accessible without a pass-phrase, i.e. it must
7686 not be encrypted. File permissions should grant read-only access to the
7687 system superuser account ("root"), and no access to anyone else.
7688 This feature is available in Postfix 2.2 and later.
7690
7692 File with the Postfix SMTP client ECDSA certificate in PEM format.
7693 This file may also contain the Postfix SMTP client ECDSA private key.
7694 With Postfix >= 3.4 the preferred way to configure client keys and cer‐
7695 tificates is via the "smtp_tls_chain_files" parameter.
7696 See the discussion under smtp_tls_cert_file for more details.
7698 Example:
7700 smtp_tls_eccert_file = /etc/postfix/ecdsa-ccert.pem
7702 This feature is available in Postfix 2.6 and later, when Postfix is
7704 compiled and linked with OpenSSL 1.0.0 or later.
7705
7707 File with the Postfix SMTP client ECDSA private key in PEM format.
7708 This file may be combined with the Postfix SMTP client ECDSA certifi‐
7709 cate file specified with $smtp_tls_eccert_file. With Postfix >= 3.4
7710 the preferred way to configure client keys and certificates is via the
7711 "smtp_tls_chain_files" parameter.
7712 The private key must be accessible without a pass-phrase, i.e. it must
7714 not be encrypted. File permissions should grant read-only access to the
7715 system superuser account ("root"), and no access to anyone else.
7716 This feature is available in Postfix 2.6 and later, when Postfix is
7718 compiled and linked with OpenSSL 1.0.0 or later.
7719
7721 With mandatory TLS encryption, require that the remote SMTP server
7722 hostname matches the information in the remote SMTP server certificate.
7723 As of RFC 2487 the requirements for hostname checking for MTA clients
7724 are not specified.
7725 This option can be set to "no" to disable strict peer name checking.
7727 This setting has no effect on sessions that are controlled via the
7728 smtp_tls_per_site table.
7729 Disabling the hostname verification can make sense in closed environ‐
7731 ment where special CAs are created. If not used carefully, this option
7732 opens the danger of a "man-in-the-middle" attack (the CommonName of
7733 this attacker will be logged).
7734 This feature is available in Postfix 2.2 and later. With Postfix 2.3
7736 and later use smtp_tls_security_level instead.
7737
7739 List of ciphers or cipher types to exclude from the Postfix SMTP client
7740 cipher list at all TLS security levels. This is not an OpenSSL ci‐
7741 pherlist, it is a simple list separated by whitespace and/or commas.
7742 The elements are a single cipher, or one or more "+" separated cipher
7743 properties, in which case only ciphers matching all the properties are
7744 excluded.
7745 Examples (some of these will cause problems):
7747 smtp_tls_exclude_ciphers = aNULL
7749 smtp_tls_exclude_ciphers = MD5, DES
7750 smtp_tls_exclude_ciphers = DES+MD5
7751 smtp_tls_exclude_ciphers = AES256-SHA, DES-CBC3-MD5
7752 smtp_tls_exclude_ciphers = kEDH+aRSA
7753 The first setting, disables anonymous ciphers. The next setting dis‐
7755 ables ciphers that use the MD5 digest algorithm or the (single) DES en‐
7756 cryption algorithm. The next setting disables ciphers that use MD5 and
7757 DES together. The next setting disables the two ciphers "AES256-SHA"
7758 and "DES-CBC3-MD5". The last setting disables ciphers that use "EDH"
7759 key exchange with RSA authentication.
7760 This feature is available in Postfix 2.3 and later.
7762
7764 List of acceptable remote SMTP server certificate fingerprints for the
7765 "fingerprint" TLS security level (smtp_tls_security_level = finger‐
7766 print). At this security level, Certification Authorities are not used,
7767 and certificate expiration times are ignored. Instead, server certifi‐
7768 cates are verified directly via their certificate fingerprint or public
7769 key fingerprint (Postfix 2.9 and later). The fingerprint is a message
7770 digest of the server certificate (or public key). The digest algorithm
7771 is selected via the smtp_tls_fingerprint_digest parameter.
7772 The colons between each pair of nibbles in the fingerprint value are
7774 optional (Postfix >= 3.6). These were required in earlier Postfix re‐
7775 leases.
7776 When an smtp_tls_policy_maps table entry specifies the "fingerprint"
7778 security level, any "match" attributes in that entry specify the list
7779 of valid fingerprints for the corresponding destination. Multiple fin‐
7780 gerprints can be combined with a "|" delimiter in a single match attri‐
7781 bute, or multiple match attributes can be employed.
7782 Example: Certificate fingerprint verification with internal mailhub.
7784 Two matching fingerprints are listed. The relayhost may be multiple
7785 physical hosts behind a load-balancer, each with its own private/public
7786 key and self-signed certificate. Alternatively, a single relayhost may
7787 be in the process of switching from one set of private/public keys to
7788 another, and both keys are trusted just prior to the transition.
7789 relayhost = [mailhub.example.com]
7791 smtp_tls_security_level = fingerprint
7792 smtp_tls_fingerprint_digest = sha256
7793 smtp_tls_fingerprint_cert_match =
7794 cd:fc:d8:db:f8:c4:82:96:6c:...:28:71:e8:f5:8d:a5:0d:9b:d4:a6
7795 dd:5c:ef:f5:c3:bc:64:25:36:...:99:36:06:ce:40:ef:de:2e:ad:a4
7796 Example: Certificate fingerprint verification with selected destina‐
7798 tions. As in the example above, we show two matching fingerprints:
7799 /etc/postfix/main.cf:
7801 smtp_tls_policy_maps = hash:/etc/postfix/tls_policy
7802 smtp_tls_fingerprint_digest = sha256
7803 /etc/postfix/tls_policy:
7805 example.com fingerprint
7806 match=51:e9:af:2e:1e:40:1f:...:64:0a:30:35:2d:09:16:31:5a:eb:82:76
7807 match=b6:b4:72:34:e2:59:cd:...:c2:ca:63:0d:4d:cc:2c:7d:84:de:e6:2f
7808 This feature is available in Postfix 2.5 and later.
7810
7812 The message digest algorithm used to construct remote SMTP server cer‐
7813 tificate fingerprints. At the "fingerprint" TLS security level
7814 (smtp_tls_security_level = fingerprint), the server certificate is ver‐
7815 ified by directly matching its certificate fingerprint or its public
7816 key fingerprint (Postfix 2.9 and later). The fingerprint is the message
7817 digest of the server certificate (or its public key) using the selected
7818 algorithm. With a digest algorithm resistant to "second pre-image" at‐
7819 tacks, it is not feasible to create a new public key and a matching
7820 certificate (or public/private key-pair) that has the same fingerprint.
7821 The default algorithm is sha256 with Postfix >= 3.6 and the compatibil‐
7823 ity_level set to 3.6 or higher. With Postfix <= 3.5, the default algo‐
7824 rithm is md5.
7825 The best-practice algorithm is now sha256. Recent advances in hash
7827 function cryptanalysis have led to md5 and sha1 being deprecated in fa‐
7828 vor of sha256. However, as long as there are no known "second pre-im‐
7829 age" attacks against the older algorithms, their use in this context,
7830 though not recommended, is still likely safe.
7831 While additional digest algorithms are often available with OpenSSL's
7833 libcrypto, only those used by libssl in SSL cipher suites are available
7834 to Postfix. You'll likely find support for md5, sha1, sha256 and
7835 sha512.
7836 To find the fingerprint of a specific certificate file, with a specific
7838 digest algorithm, run:
7839 $ openssl x509 -noout -fingerprint -digest -in certfile.pem
7841 The text to the right of "=" sign is the desired fingerprint. For ex‐
7843 ample:
7844 $ openssl x509 -noout -fingerprint -sha256 -in cert.pem
7846 SHA256 Fingerprint=D4:6A:AB:19:24:...:BB:A6:CB:66:82:C0:8E:9B:EE:29:A8:1A
7847 To extract the public key fingerprint from an X.509 certificate, you
7849 need to extract the public key from the certificate and compute the ap‐
7850 propriate digest of its DER (ASN.1) encoding. With OpenSSL the "-pub‐
7851 key" option of the "x509" command extracts the public key always in
7852 "PEM" format. We pipe the result to another OpenSSL command that con‐
7853 verts the key to DER and then to the "dgst" command to compute the fin‐
7854 gerprint.
7855 The actual command to transform the key to DER format depends on the
7857 version of OpenSSL used. As of OpenSSL 1.0.0, the "pkey" command sup‐
7858 ports all key types.
7859 # OpenSSL >= 1.0 with SHA-256 fingerprints.
7861 $ openssl x509 -in cert.pem -noout -pubkey |
7862 openssl pkey -pubin -outform DER |
7863 openssl dgst -sha256 -c
7864 (stdin)= 64:3f:1f:f6:e5:1e:d4:2a:56:...:fc:09:1a:61:98:b5:bc:7c:60:58
7865 The Postfix SMTP server and client log the peer (leaf) certificate fin‐
7867 gerprint and public key fingerprint when the TLS loglevel is 2 or
7868 higher.
7869 This feature is available in Postfix 2.5 and later.
7871
7873 Lookup the associated DANE TLSA RRset even when a hostname is not an
7874 alias and its address records lie in an unsigned zone. This is un‐
7875 likely to ever yield DNSSEC validated results, since child zones of un‐
7876 signed zones are also unsigned in the absence of DLV or locally config‐
7877 ured non-root trust-anchors. We anticipate that such mechanisms will
7878 not be used for just the "_tcp" subdomain of a host. Suppressing the
7879 TLSA RRset lookup reduces latency and avoids potential interoperability
7880 problems with nameservers for unsigned zones that are not prepared to
7881 handle the new TLSA RRset.
7882 This feature is available in Postfix 2.11.
7884
7886 File with the Postfix SMTP client RSA private key in PEM format. This
7887 file may be combined with the Postfix SMTP client RSA certificate file
7888 specified with $smtp_tls_cert_file. With Postfix >= 3.4 the preferred
7889 way to configure client keys and certificates is via the
7890 "smtp_tls_chain_files" parameter.
7891 The private key must be accessible without a pass-phrase, i.e. it must
7893 not be encrypted. File permissions should grant read-only access to the
7894 system superuser account ("root"), and no access to anyone else.
7895 Example:
7897 smtp_tls_key_file = $smtp_tls_cert_file
7899 This feature is available in Postfix 2.2 and later.
7901
7903 Enable additional Postfix SMTP client logging of TLS activity. Each
7904 logging level also includes the information that is logged at a lower
7905 logging level.
7906 0 Disable logging of TLS activity.
7908 1 Log only a summary message on TLS handshake completion - no
7910 logging of remote SMTP server certificate trust-chain verifica‐
7911 tion errors if server certificate verification is not required.
7912 With Postfix 2.8 and earlier, log the summary message and uncon‐
7913 ditionally log trust-chain verification errors.
7914 2 Also log levels during TLS negotiation.
7916 3 Also log hexadecimal and ASCII dump of TLS negotiation
7918 process.
7919 4 Also log hexadecimal and ASCII dump of complete transmission
7921 after STARTTLS.
7922 Do not use "smtp_tls_loglevel = 2" or higher except in case of prob‐
7924 lems. Use of loglevel 4 is strongly discouraged.
7925 This feature is available in Postfix 2.2 and later.
7927
7929 The minimum TLS cipher grade that the Postfix SMTP client will use with
7930 mandatory TLS encryption. The default value "medium" is suitable for
7931 most destinations with which you may want to enforce TLS, and is beyond
7932 the reach of today's cryptanalytic methods. See smtp_tls_policy_maps
7933 for information on how to configure ciphers on a per-destination basis.
7934 The following cipher grades are supported:
7936 export Enable "EXPORT" grade or better OpenSSL ciphers. The underlying
7938 cipherlist is specified via the tls_export_cipherlist configura‐
7939 tion parameter, which you are strongly encouraged to not change.
7940 This choice is insecure and SHOULD NOT be used.
7941 low Enable "LOW" grade or better OpenSSL ciphers. The underlying
7943 cipherlist is specified via the tls_low_cipherlist configuration
7944 parameter, which you are strongly encouraged to not change.
7945 This choice is insecure and SHOULD NOT be used.
7946 medium Enable "MEDIUM" grade or better OpenSSL ciphers. The underlying
7948 cipherlist is specified via the tls_medium_cipherlist configura‐
7949 tion parameter, which you are strongly encouraged to not change.
7950 high Enable only "HIGH" grade OpenSSL ciphers. This setting may be
7952 appropriate when all mandatory TLS destinations (e.g. when all
7953 mail is routed to a suitably capable relayhost) support at least
7954 one "HIGH" grade cipher. The underlying cipherlist is specified
7955 via the tls_high_cipherlist configuration parameter, which you
7956 are strongly encouraged to not change.
7957 null Enable only the "NULL" OpenSSL ciphers, these provide authenti‐
7959 cation without encryption. This setting is only appropriate in
7960 the rare case that all servers are prepared to use NULL ciphers
7961 (not normally enabled in TLS servers). A plausible use-case is
7962 an LMTP server listening on a UNIX-domain socket that is config‐
7963 ured to support "NULL" ciphers. The underlying cipherlist is
7964 specified via the tls_null_cipherlist configuration parameter,
7965 which you are strongly encouraged to not change.
7966 The underlying cipherlists for grades other than "null" include anony‐
7968 mous ciphers, but these are automatically filtered out if the Postfix
7969 SMTP client is configured to verify server certificates. You are very
7970 unlikely to need to take any steps to exclude anonymous ciphers, they
7971 are excluded automatically as necessary. If you must exclude anonymous
7972 ciphers at the "may" or "encrypt" security levels, when the Postfix
7973 SMTP client does not need or use peer certificates, set "smtp_tls_ex‐
7974 clude_ciphers = aNULL". To exclude anonymous ciphers only when TLS is
7975 enforced, set "smtp_tls_mandatory_exclude_ciphers = aNULL".
7976 This feature is available in Postfix 2.3 and later.
7978
7980 Additional list of ciphers or cipher types to exclude from the Postfix
7981 SMTP client cipher list at mandatory TLS security levels. This list
7982 works in addition to the exclusions listed with smtp_tls_exclude_ci‐
7983 phers (see there for syntax details).
7984 Starting with Postfix 2.6, the mandatory cipher exclusions can be spec‐
7986 ified on a per-destination basis via the TLS policy "exclude" attri‐
7987 bute. See smtp_tls_policy_maps for notes and examples.
7988 This feature is available in Postfix 2.3 and later.
7990
7992 TLS protocols that the Postfix SMTP client will use with mandatory TLS
7993 encryption. In main.cf the values are separated by whitespace, commas
7994 or colons. In the policy table "protocols" attribute (see smtp_tls_pol‐
7995 icy_maps) the only valid separator is colon. An empty value means allow
7996 all protocols.
7997 The valid protocol names (see SSL_get_version(3)) are "SSLv2", "SSLv3",
7999 "TLSv1", "TLSv1.1", "TLSv1.2" and "TLSv1.3". Starting with Postfix
8000 3.6, the default value is ">=TLSv1", which sets TLS 1.0 as the lowest
8001 supported TLS protocol version (see below). Older releases use the "!"
8002 exclusion syntax, also described below.
8003 As of Postfix 3.6, the preferred way to limit the range of acceptable
8005 protocols is to set a lowest acceptable TLS protocol version and/or a
8006 highest acceptable TLS protocol version. To set the lower bound in‐
8007 clude an element of the form: ">=version" where version is a either one
8008 of the TLS protocol names listed above, or a hexadecimal number corre‐
8009 sponding to the desired TLS protocol version (0301 for TLS 1.0, 0302
8010 for TLS 1.1, etc.). For the upper bound, use "<=version". There must
8011 be no whitespace between the ">=" or "<=" symbols and the protocol name
8012 or number.
8013 Hexadecimal protocol numbers make it possible to specify protocol
8015 bounds for TLS versions that are known to OpenSSL, but might not be
8016 known to Postfix. They cannot be used with the legacy exclusion syn‐
8017 tax. Leading "0" or "0x" prefixes are supported, but not required.
8018 Therefore, "301", "0301", "0x301" and "0x0301" are all equivalent to
8019 "TLSv1". Hexadecimal versions unknown to OpenSSL will fail to set the
8020 upper or lower bound, and a warning will be logged. Hexadecimal ver‐
8021 sions should only be used when Postfix is linked with some future ver‐
8022 sion of OpenSSL that supports TLS 1.4 or later, but Postfix does not
8023 yet support a symbolic name for that protocol version.
8024 Hexadecimal example (Postfix >= 3.6):
8026 # Allow only TLS 1.2 through (hypothetical) TLS 1.4, once supported
8028 # in some future version of OpenSSL (presently a warning is logged).
8029 smtp_tls_mandatory_protocols = >=TLSv1.2, <=0305
8030 # Allow only TLS 1.2 and up:
8031 smtp_tls_mandatory_protocols = >=0x0303
8032 With Postfix < 3.6 there is no support for a minimum or maximum ver‐
8034 sion, and the protocol range is configured via protocol exclusions. To
8035 require at least TLS 1.0, set "smtp_tls_mandatory_protocols = !SSLv2,
8036 !SSLv3". Listing the protocols to include, rather than protocols to ex‐
8037 clude, is supported, but not recommended. The exclusion syntax more
8038 accurately matches the underlying OpenSSL interface.
8039 When using the exclusion syntax, take care to ensure that the range of
8041 protocols supported by the Postfix SMTP client is contiguous. When a
8042 protocol version is enabled, disabling any higher version implicitly
8043 disables all versions above that higher version. Thus, for example:
8044 smtp_tls_mandatory_protocols = !SSLv2, !SSLv3, !TLSv1.1
8046 also disables any protocols version higher than TLSv1.1 leaving only
8048 "TLSv1" enabled.
8049 Support for "TLSv1.3" was introduced in OpenSSL 1.1.1. Disabling this
8051 protocol via "!TLSv1.3" is supported since Postfix 3.4 (or patch re‐
8052 leases >= 3.0.14, 3.1.10, 3.2.7 and 3.3.2).
8053 While the vast majority of SMTP servers with DANE TLSA records now sup‐
8055 port at least TLS 1.2, a few still only support TLS 1.0. If you use
8056 "dane" or "dane-only" it is best to not disable TLSv1, except perhaps
8057 via the policy table for destinations which you are sure will support
8058 "TLSv1.2".
8059 See the documentation of the smtp_tls_policy_maps parameter and
8061 TLS_README for more information about security levels.
8062 Example:
8064 # Preferred syntax with Postfix >= 3.6:
8065 smtp_tls_mandatory_protocols = >=TLSv1.2, <=TLSv1.3
8066 # Legacy syntax:
8067 smtp_tls_mandatory_protocols = !SSLv2, !SSLv3, !TLSv1, !TLSv1.1
8068 This feature is available in Postfix 2.3 and later.
8070
8072 Log the hostname of a remote SMTP server that offers STARTTLS, when TLS
8073 is not already enabled for that server.
8074 The logfile record looks like:
8076 postfix/smtp[pid]: Host offered STARTTLS: [name.of.host]
8078 This feature is available in Postfix 2.2 and later.
8080
8082 Optional lookup tables with the Postfix SMTP client TLS usage policy by
8083 next-hop destination and by remote SMTP server hostname. When both
8084 lookups succeed, the more specific per-site policy (NONE, MUST, etc)
8085 overrides the less specific one (MAY), and the more secure per-site
8086 policy (MUST, etc) overrides the less secure one (NONE). With Postfix
8087 2.3 and later smtp_tls_per_site is strongly discouraged: use
8088 smtp_tls_policy_maps instead.
8089 Use of the bare hostname as the per-site table lookup key is discour‐
8091 aged. Always use the full destination nexthop (enclosed in [] with a
8092 possible ":port" suffix). A recipient domain or MX-enabled transport
8093 next-hop with no port suffix may look like a bare hostname, but is
8094 still a suitable destination.
8095 Specify a next-hop destination or server hostname on the left-hand
8097 side; no wildcards are allowed. The next-hop destination is either the
8098 recipient domain, or the destination specified with a transport(5) ta‐
8099 ble, the relayhost parameter, or the relay_transport parameter. On the
8100 right hand side specify one of the following keywords:
8101 NONE Don't use TLS at all. This overrides a less specific MAY lookup
8103 result from the alternate host or next-hop lookup key, and over‐
8104 rides the global smtp_use_tls, smtp_enforce_tls, and
8105 smtp_tls_enforce_peername settings.
8106 MAY Try to use TLS if the server announces support, otherwise use
8108 the unencrypted connection. This has less precedence than a more
8109 specific result (including NONE) from the alternate host or
8110 next-hop lookup key, and has less precedence than the more spe‐
8111 cific global "smtp_enforce_tls = yes" or "smtp_tls_enforce_peer‐
8112 name = yes".
8113 MUST_NOPEERMATCH
8115 Require TLS encryption, but do not require that the remote SMTP
8116 server hostname matches the information in the remote SMTP
8117 server certificate, or that the server certificate was issued by
8118 a trusted CA. This overrides a less secure NONE or a less spe‐
8119 cific MAY lookup result from the alternate host or next-hop
8120 lookup key, and overrides the global smtp_use_tls, smtp_en‐
8121 force_tls and smtp_tls_enforce_peername settings.
8122 MUST Require TLS encryption, require that the remote SMTP server
8124 hostname matches the information in the remote SMTP server cer‐
8125 tificate, and require that the remote SMTP server certificate
8126 was issued by a trusted CA. This overrides a less secure NONE
8127 and MUST_NOPEERMATCH or a less specific MAY lookup result from
8128 the alternate host or next-hop lookup key, and overrides the
8129 global smtp_use_tls, smtp_enforce_tls and smtp_tls_enforce_peer‐
8130 name settings.
8131 The above keywords correspond to the "none", "may", "encrypt" and "ver‐
8133 ify" security levels for the new smtp_tls_security_level parameter in‐
8134 troduced in Postfix 2.3. Starting with Postfix 2.3, and independently
8135 of how the policy is specified, the smtp_tls_mandatory_ciphers and
8136 smtp_tls_mandatory_protocols parameters apply when TLS encryption is
8137 mandatory. Connections for which encryption is optional typically en‐
8138 able all "export" grade and better ciphers (see smtp_tls_ciphers and
8139 smtp_tls_protocols).
8140 As long as no secure DNS lookup mechanism is available, false hostnames
8142 in MX or CNAME responses can change the server hostname that Postfix
8143 uses for TLS policy lookup and server certificate verification. Even
8144 with a perfect match between the server hostname and the server cer‐
8145 tificate, there is no guarantee that Postfix is connected to the right
8146 server. See TLS_README (Closing a DNS loophole with obsolete per-site
8147 TLS policies) for a possible work-around.
8148 This feature is available in Postfix 2.2 and later. With Postfix 2.3
8150 and later use smtp_tls_policy_maps instead.
8151
8153 Optional lookup tables with the Postfix SMTP client TLS security policy
8154 by next-hop destination; when a non-empty value is specified, this
8155 overrides the obsolete smtp_tls_per_site parameter. See TLS_README for
8156 a more detailed discussion of TLS security levels.
8157 Specify zero or more "type:name" lookup tables, separated by whitespace
8159 or comma. Tables will be searched in the specified order until a match
8160 is found.
8161 The TLS policy table is indexed by the full next-hop destination, which
8163 is either the recipient domain, or the verbatim next-hop specified in
8164 the transport table, $local_transport, $virtual_transport, $re‐
8165 lay_transport or $default_transport. This includes any enclosing square
8166 brackets and any non-default destination server port suffix. The LMTP
8167 socket type prefix (inet: or unix:) is not included in the lookup key.
8168 Only the next-hop domain, or $myhostname with LMTP over UNIX-domain
8170 sockets, is used as the nexthop name for certificate verification. The
8171 port and any enclosing square brackets are used in the table lookup
8172 key, but are not used for server name verification.
8173 When the lookup key is a domain name without enclosing square brackets
8175 or any :port suffix (typically the recipient domain), and the full do‐
8176 main is not found in the table, just as with the transport(5) table,
8177 the parent domain starting with a leading "." is matched recursively.
8178 This allows one to specify a security policy for a recipient domain and
8179 all its sub-domains.
8180 The lookup result is a security level, followed by an optional list of
8182 whitespace and/or comma separated name=value attributes that override
8183 related main.cf settings. The TLS security levels in order of increas‐
8184 ing security are:
8185 none No TLS. No additional attributes are supported at this level.
8187 may Opportunistic TLS. Since sending in the clear is acceptable, de‐
8189 manding stronger than default TLS security merely reduces inter‐
8190 operability. The optional "ciphers", "exclude", and "protocols"
8191 attributes (available for opportunistic TLS with Postfix >= 2.6)
8192 and "connection_reuse" attribute (Postfix >= 3.4) override the
8193 "smtp_tls_ciphers", "smtp_tls_exclude_ciphers", "smtp_tls_proto‐
8194 cols", and "smtp_tls_connection_reuse" configuration parameters.
8195 When opportunistic TLS handshakes fail, Postfix retries the con‐
8196 nection with TLS disabled. This allows mail delivery to sites
8197 with non-interoperable TLS implementations.
8198 encrypt
8200 Mandatory TLS encryption. At this level and higher, the optional
8201 "protocols" attribute overrides the main.cf smtp_tls_manda‐
8202 tory_protocols parameter, the optional "ciphers" attribute over‐
8203 rides the main.cf smtp_tls_mandatory_ciphers parameter, the op‐
8204 tional "exclude" attribute (Postfix >= 2.6) overrides the
8205 main.cf smtp_tls_mandatory_exclude_ciphers parameter, and the
8206 optional "connection_reuse" attribute (Postfix >= 3.4) overrides
8207 the main.cf smtp_tls_connection_reuse parameter. In the policy
8208 table, multiple protocols or excluded ciphers must be separated
8209 by colons, as attribute values may not contain whitespace or
8210 commas.
8211 dane Opportunistic DANE TLS. The TLS policy for the destination is
8213 obtained via TLSA records in DNSSEC. If no TLSA records are
8214 found, the effective security level used is may. If TLSA
8215 records are found, but none are usable, the effective security
8216 level is encrypt. When usable TLSA records are obtained for the
8217 remote SMTP server, the server certificate must match the TLSA
8218 records. RFC 7672 (DANE) TLS authentication and DNSSEC support
8219 is available with Postfix 2.11 and later. The optional "connec‐
8220 tion_reuse" attribute (Postfix >= 3.4) overrides the main.cf
8221 smtp_tls_connection_reuse parameter.
8222 dane-only
8224 Mandatory DANE TLS. The TLS policy for the destination is ob‐
8225 tained via TLSA records in DNSSEC. If no TLSA records are
8226 found, or none are usable, no connection is made to the server.
8227 When usable TLSA records are obtained for the remote SMTP
8228 server, the server certificate must match the TLSA records. RFC
8229 7672 (DANE) TLS authentication and DNSSEC support is available
8230 with Postfix 2.11 and later. The optional "connection_reuse" at‐
8231 tribute (Postfix >= 3.4) overrides the main.cf smtp_tls_connec‐
8232 tion_reuse parameter.
8233 fingerprint
8235 Certificate fingerprint verification. Available with Postfix 2.5
8236 and later. At this security level, there are no trusted Certifi‐
8237 cation Authorities. The certificate trust chain, expiration
8238 date, ... are not checked. Instead, the optional match attri‐
8239 bute, or else the main.cf smtp_tls_fingerprint_cert_match param‐
8240 eter, lists the certificate fingerprints or the public key fin‐
8241 gerprint (Postfix 2.9 and later) of the valid server certifi‐
8242 cate. The digest algorithm used to calculate the fingerprint is
8243 selected by the smtp_tls_fingerprint_digest parameter. Multiple
8244 fingerprints can be combined with a "|" delimiter in a single
8245 match attribute, or multiple match attributes can be employed.
8246 The ":" character is not used as a delimiter as it occurs be‐
8247 tween each pair of fingerprint (hexadecimal) digits. The op‐
8248 tional "connection_reuse" attribute (Postfix >= 3.4) overrides
8249 the main.cf smtp_tls_connection_reuse parameter.
8250 verify Mandatory TLS verification. At this security level, DNS MX
8252