1SMTP(8) System Manager's Manual SMTP(8)
2
6 smtp - Postfix SMTP+LMTP client
7
9 smtp [generic Postfix daemon options]
10
12 The Postfix SMTP+LMTP client implements the SMTP and LMTP mail delivery
13 protocols. It processes message delivery requests from the queue man‐
14 ager. Each request specifies a queue file, a sender address, a domain
15 or host to deliver to, and recipient information. This program expects
16 to be run from the master(8) process manager.
17 The SMTP+LMTP client updates the queue file and marks recipients as
19 finished, or it informs the queue manager that delivery should be tried
20 again at a later time. Delivery status reports are sent to the
21 bounce(8), defer(8) or trace(8) daemon as appropriate.
22 The SMTP+LMTP client looks up a list of mail exchanger addresses for
24 the destination host, sorts the list by preference, and connects to
25 each listed address until it finds a server that responds.
26 When a server is not reachable, or when mail delivery fails due to a
28 recoverable error condition, the SMTP+LMTP client will try to deliver
29 the mail to an alternate host.
30 After a successful mail transaction, a connection may be saved to the
32 scache(8) connection cache server, so that it may be used by any
33 SMTP+LMTP client for a subsequent transaction.
34 By default, connection caching is enabled temporarily for destinations
36 that have a high volume of mail in the active queue. Connection caching
37 can be enabled permanently for specific destinations.
38
40 SMTP destinations have the following form:
41 domainname
43 domainname:port
45 Look up the mail exchangers for the specified domain, and con‐
46 nect to the specified port (default: smtp).
47 [hostname]
49 [hostname]:port
51 Look up the address(es) of the specified host, and connect to
52 the specified port (default: smtp).
53 [address]
55 [address]:port
57 Connect to the host at the specified address, and connect to the
58 specified port (default: smtp). An IPv6 address must be format‐
59 ted as [ipv6:address].
60
62 LMTP destinations have the following form:
63 unix:pathname
65 Connect to the local UNIX-domain server that is bound to the
66 specified pathname. If the process runs chrooted, an absolute
67 pathname is interpreted relative to the Postfix queue directory.
68 inet:hostname
70 inet:hostname:port
72 inet:[address]
74 inet:[address]:port
76 Connect to the specified TCP port on the specified local or
77 remote host. If no port is specified, connect to the port
78 defined as lmtp in services(4). If no such service is found,
79 the lmtp_tcp_port configuration parameter (default value of 24)
80 will be used. An IPv6 address must be formatted as
81 [ipv6:address].
82
84 The SMTP+LMTP client is moderately security-sensitive. It talks to SMTP
85 or LMTP servers and to DNS servers on the network. The SMTP+LMTP client
86 can be run chrooted at fixed low privilege.
87
89 RFC 821 (SMTP protocol)
90 RFC 822 (ARPA Internet Text Messages)
91 RFC 1651 (SMTP service extensions)
92 RFC 1652 (8bit-MIME transport)
93 RFC 1870 (Message Size Declaration)
94 RFC 2033 (LMTP protocol)
95 RFC 2034 (SMTP Enhanced Error Codes)
96 RFC 2045 (MIME: Format of Internet Message Bodies)
97 RFC 2046 (MIME: Media Types)
98 RFC 2554 (AUTH command)
99 RFC 2821 (SMTP protocol)
100 RFC 2920 (SMTP Pipelining)
101 RFC 3207 (STARTTLS command)
102 RFC 3461 (SMTP DSN Extension)
103 RFC 3463 (Enhanced Status Codes)
104 RFC 4954 (AUTH command)
105 RFC 5321 (SMTP protocol)
106 RFC 6531 (Internationalized SMTP)
107 RFC 6533 (Internationalized Delivery Status Notifications)
108 RFC 7672 (SMTP security via opportunistic DANE TLS)
109
111 Problems and transactions are logged to syslogd(8) or postlogd(8).
112 Corrupted message files are marked so that the queue manager can move
113 them to the corrupt queue for further inspection.
114 Depending on the setting of the notify_classes parameter, the postmas‐
116 ter is notified of bounces, protocol problems, and of other trouble.
117
119 SMTP and LMTP connection caching does not work with TLS. The necessary
120 support for TLS object passivation and re-activation does not exist
121 without closing the session, which defeats the purpose.
122 SMTP and LMTP connection caching assumes that SASL credentials are
124 valid for all destinations that map onto the same IP address and TCP
125 port.
126
128 Before Postfix version 2.3, the LMTP client is a separate program that
129 implements only a subset of the functionality available with SMTP:
130 there is no support for TLS, and connections are cached in-process,
131 making it ineffective when the client is used for multiple domains.
132 Most smtp_xxx configuration parameters have an lmtp_xxx "mirror" param‐
134 eter for the equivalent LMTP feature. This document describes only
135 those LMTP-related parameters that aren't simply "mirror" parameters.
136 Changes to main.cf are picked up automatically, as smtp(8) processes
138 run for only a limited amount of time. Use the command "postfix reload"
139 to speed up a change.
140 The text below provides only a parameter summary. See postconf(5) for
142 more details including examples.
143
145 ignore_mx_lookup_error (no)
146 Ignore DNS MX lookups that produce no response.
147 smtp_always_send_ehlo (yes)
149 Always send EHLO at the start of an SMTP session.
150 smtp_never_send_ehlo (no)
152 Never send EHLO at the start of an SMTP session.
153 smtp_defer_if_no_mx_address_found (no)
155 Defer mail delivery when no MX record resolves to an IP address.
156 smtp_line_length_limit (998)
158 The maximal length of message header and body lines that Postfix
159 will send via SMTP.
160 smtp_pix_workaround_delay_time (10s)
162 How long the Postfix SMTP client pauses before sending
163 ".<CR><LF>" in order to work around the PIX firewall
164 "<CR><LF>.<CR><LF>" bug.
165 smtp_pix_workaround_threshold_time (500s)
167 How long a message must be queued before the Postfix SMTP client
168 turns on the PIX firewall "<CR><LF>.<CR><LF>" bug workaround for
169 delivery through firewalls with "smtp fixup" mode turned on.
170 smtp_pix_workarounds (disable_esmtp, delay_dotcrlf)
172 A list that specifies zero or more workarounds for CISCO PIX
173 firewall bugs.
174 smtp_pix_workaround_maps (empty)
176 Lookup tables, indexed by the remote SMTP server address, with
177 per-destination workarounds for CISCO PIX firewall bugs.
178 smtp_quote_rfc821_envelope (yes)
180 Quote addresses in Postfix SMTP client MAIL FROM and RCPT TO
181 commands as required by RFC 5321.
182 smtp_reply_filter (empty)
184 A mechanism to transform replies from remote SMTP servers one
185 line at a time.
186 smtp_skip_5xx_greeting (yes)
188 Skip remote SMTP servers that greet with a 5XX status code.
189 smtp_skip_quit_response (yes)
191 Do not wait for the response to the SMTP QUIT command.
192 Available in Postfix version 2.0 and earlier:
194 smtp_skip_4xx_greeting (yes)
196 Skip SMTP servers that greet with a 4XX status code (go away,
197 try again later).
198 Available in Postfix version 2.2 and later:
200 smtp_discard_ehlo_keyword_address_maps (empty)
202 Lookup tables, indexed by the remote SMTP server address, with
203 case insensitive lists of EHLO keywords (pipelining, starttls,
204 auth, etc.) that the Postfix SMTP client will ignore in the EHLO
205 response from a remote SMTP server.
206 smtp_discard_ehlo_keywords (empty)
208 A case insensitive list of EHLO keywords (pipelining, starttls,
209 auth, etc.) that the Postfix SMTP client will ignore in the EHLO
210 response from a remote SMTP server.
211 smtp_generic_maps (empty)
213 Optional lookup tables that perform address rewriting in the
214 Postfix SMTP client, typically to transform a locally valid
215 address into a globally valid address when sending mail across
216 the Internet.
217 Available in Postfix version 2.2.9 and later:
219 smtp_cname_overrides_servername (version dependent)
221 When the remote SMTP servername is a DNS CNAME, replace the
222 servername with the result from CNAME expansion for the purpose
223 of logging, SASL password lookup, TLS policy decisions, or TLS
224 certificate verification.
225 Available in Postfix version 2.3 and later:
227 lmtp_discard_lhlo_keyword_address_maps (empty)
229 Lookup tables, indexed by the remote LMTP server address, with
230 case insensitive lists of LHLO keywords (pipelining, starttls,
231 auth, etc.) that the Postfix LMTP client will ignore in the LHLO
232 response from a remote LMTP server.
233 lmtp_discard_lhlo_keywords (empty)
235 A case insensitive list of LHLO keywords (pipelining, starttls,
236 auth, etc.) that the Postfix LMTP client will ignore in the LHLO
237 response from a remote LMTP server.
238 Available in Postfix version 2.4.4 and later:
240 send_cyrus_sasl_authzid (no)
242 When authenticating to a remote SMTP or LMTP server with the
243 default setting "no", send no SASL authoriZation ID (authzid);
244 send only the SASL authentiCation ID (authcid) plus the auth‐
245 cid's password.
246 Available in Postfix version 2.5 and later:
248 smtp_header_checks (empty)
250 Restricted header_checks(5) tables for the Postfix SMTP client.
251 smtp_mime_header_checks (empty)
253 Restricted mime_header_checks(5) tables for the Postfix SMTP
254 client.
255 smtp_nested_header_checks (empty)
257 Restricted nested_header_checks(5) tables for the Postfix SMTP
258 client.
259 smtp_body_checks (empty)
261 Restricted body_checks(5) tables for the Postfix SMTP client.
262 Available in Postfix version 2.6 and later:
264 tcp_windowsize (0)
266 An optional workaround for routers that break TCP window scal‐
267 ing.
268 Available in Postfix version 2.8 and later:
270 smtp_dns_resolver_options (empty)
272 DNS Resolver options for the Postfix SMTP client.
273 Available in Postfix version 2.9 and later:
275 smtp_per_record_deadline (no)
277 Change the behavior of the smtp_*_timeout time limits, from a
278 time limit per read or write system call, to a time limit to
279 send or receive a complete record (an SMTP command line, SMTP
280 response line, SMTP message content line, or TLS protocol mes‐
281 sage).
282 smtp_send_dummy_mail_auth (no)
284 Whether or not to append the "AUTH=<>" option to the MAIL FROM
285 command in SASL-authenticated SMTP sessions.
286 Available in Postfix version 2.11 and later:
288 smtp_dns_support_level (empty)
290 Level of DNS support in the Postfix SMTP client.
291 Available in Postfix version 3.0 and later:
293 smtp_delivery_status_filter ($default_delivery_status_filter)
295 Optional filter for the smtp(8) delivery agent to change the
296 delivery status code or explanatory text of successful or unsuc‐
297 cessful deliveries.
298 smtp_dns_reply_filter (empty)
300 Optional filter for Postfix SMTP client DNS lookup results.
301 Available in Postfix version 3.3 and later:
303 smtp_balance_inet_protocols (yes)
305 When a remote destination resolves to a combination of IPv4 and
306 IPv6 addresses, ensure that the Postfix SMTP client can try both
307 address types before it runs into the smtp_mx_address_limit.
308
310 Available in Postfix version 2.0 and later:
311 disable_mime_output_conversion (no)
313 Disable the conversion of 8BITMIME format to 7BIT format.
314 mime_boundary_length_limit (2048)
316 The maximal length of MIME multipart boundary strings.
317 mime_nesting_limit (100)
319 The maximal recursion level that the MIME processor will handle.
320
322 Available in Postfix version 2.1 and later:
323 smtp_send_xforward_command (no)
325 Send the non-standard XFORWARD command when the Postfix SMTP
326 server EHLO response announces XFORWARD support.
327
329 smtp_sasl_auth_enable (no)
330 Enable SASL authentication in the Postfix SMTP client.
331 smtp_sasl_password_maps (empty)
333 Optional Postfix SMTP client lookup tables with one user‐
334 name:password entry per sender, remote hostname or next-hop
335 domain.
336 smtp_sasl_security_options (noplaintext, noanonymous)
338 Postfix SMTP client SASL security options; as of Postfix 2.3 the
339 list of available features depends on the SASL client implemen‐
340 tation that is selected with smtp_sasl_type.
341 Available in Postfix version 2.2 and later:
343 smtp_sasl_mechanism_filter (empty)
345 If non-empty, a Postfix SMTP client filter for the remote SMTP
346 server's list of offered SASL mechanisms.
347 Available in Postfix version 2.3 and later:
349 smtp_sender_dependent_authentication (no)
351 Enable sender-dependent authentication in the Postfix SMTP
352 client; this is available only with SASL authentication, and
353 disables SMTP connection caching to ensure that mail from dif‐
354 ferent senders will use the appropriate credentials.
355 smtp_sasl_path (empty)
357 Implementation-specific information that the Postfix SMTP client
358 passes through to the SASL plug-in implementation that is
359 selected with smtp_sasl_type.
360 smtp_sasl_type (cyrus)
362 The SASL plug-in type that the Postfix SMTP client should use
363 for authentication.
364 Available in Postfix version 2.5 and later:
366 smtp_sasl_auth_cache_name (empty)
368 An optional table to prevent repeated SASL authentication fail‐
369 ures with the same remote SMTP server hostname, username and
370 password.
371 smtp_sasl_auth_cache_time (90d)
373 The maximal age of an smtp_sasl_auth_cache_name entry before it
374 is removed.
375 smtp_sasl_auth_soft_bounce (yes)
377 When a remote SMTP server rejects a SASL authentication request
378 with a 535 reply code, defer mail delivery instead of returning
379 mail as undeliverable.
380 Available in Postfix version 2.9 and later:
382 smtp_send_dummy_mail_auth (no)
384 Whether or not to append the "AUTH=<>" option to the MAIL FROM
385 command in SASL-authenticated SMTP sessions.
386
388 Detailed information about STARTTLS configuration may be found in the
389 TLS_README document.
390 smtp_tls_security_level (empty)
392 The default SMTP TLS security level for the Postfix SMTP client;
393 when a non-empty value is specified, this overrides the obsolete
394 parameters smtp_use_tls, smtp_enforce_tls, and
395 smtp_tls_enforce_peername.
396 smtp_sasl_tls_security_options ($smtp_sasl_security_options)
398 The SASL authentication security options that the Postfix SMTP
399 client uses for TLS encrypted SMTP sessions.
400 smtp_starttls_timeout (300s)
402 Time limit for Postfix SMTP client write and read operations
403 during TLS startup and shutdown handshake procedures.
404 smtp_tls_CAfile (empty)
406 A file containing CA certificates of root CAs trusted to sign
407 either remote SMTP server certificates or intermediate CA cer‐
408 tificates.
409 smtp_tls_CApath (empty)
411 Directory with PEM format Certification Authority certificates
412 that the Postfix SMTP client uses to verify a remote SMTP server
413 certificate.
414 smtp_tls_cert_file (empty)
416 File with the Postfix SMTP client RSA certificate in PEM format.
417 smtp_tls_mandatory_ciphers (medium)
419 The minimum TLS cipher grade that the Postfix SMTP client will
420 use with mandatory TLS encryption.
421 smtp_tls_exclude_ciphers (empty)
423 List of ciphers or cipher types to exclude from the Postfix SMTP
424 client cipher list at all TLS security levels.
425 smtp_tls_mandatory_exclude_ciphers (empty)
427 Additional list of ciphers or cipher types to exclude from the
428 Postfix SMTP client cipher list at mandatory TLS security lev‐
429 els.
430 smtp_tls_dcert_file (empty)
432 File with the Postfix SMTP client DSA certificate in PEM format.
433 smtp_tls_dkey_file ($smtp_tls_dcert_file)
435 File with the Postfix SMTP client DSA private key in PEM format.
436 smtp_tls_key_file ($smtp_tls_cert_file)
438 File with the Postfix SMTP client RSA private key in PEM format.
439 smtp_tls_loglevel (0)
441 Enable additional Postfix SMTP client logging of TLS activity.
442 smtp_tls_note_starttls_offer (no)
444 Log the hostname of a remote SMTP server that offers STARTTLS,
445 when TLS is not already enabled for that server.
446 smtp_tls_policy_maps (empty)
448 Optional lookup tables with the Postfix SMTP client TLS security
449 policy by next-hop destination; when a non-empty value is speci‐
450 fied, this overrides the obsolete smtp_tls_per_site parameter.
451 smtp_tls_mandatory_protocols (!SSLv2, !SSLv3)
453 List of SSL/TLS protocols that the Postfix SMTP client will use
454 with mandatory TLS encryption.
455 smtp_tls_scert_verifydepth (9)
457 The verification depth for remote SMTP server certificates.
458 smtp_tls_secure_cert_match (nexthop, dot-nexthop)
460 How the Postfix SMTP client verifies the server certificate
461 peername for the "secure" TLS security level.
462 smtp_tls_session_cache_database (empty)
464 Name of the file containing the optional Postfix SMTP client TLS
465 session cache.
466 smtp_tls_session_cache_timeout (3600s)
468 The expiration time of Postfix SMTP client TLS session cache
469 information.
470 smtp_tls_verify_cert_match (hostname)
472 How the Postfix SMTP client verifies the server certificate
473 peername for the "verify" TLS security level.
474 tls_daemon_random_bytes (32)
476 The number of pseudo-random bytes that an smtp(8) or smtpd(8)
477 process requests from the tlsmgr(8) server in order to seed its
478 internal pseudo random number generator (PRNG).
479 tls_high_cipherlist (see 'postconf -d' output)
481 The OpenSSL cipherlist for "high" grade ciphers.
482 tls_medium_cipherlist (see 'postconf -d' output)
484 The OpenSSL cipherlist for "medium" or higher grade ciphers.
485 tls_low_cipherlist (see 'postconf -d' output)
487 The OpenSSL cipherlist for "low" or higher grade ciphers.
488 tls_export_cipherlist (see 'postconf -d' output)
490 The OpenSSL cipherlist for "export" or higher grade ciphers.
491 tls_null_cipherlist (eNULL:!aNULL)
493 The OpenSSL cipherlist for "NULL" grade ciphers that provide
494 authentication without encryption.
495 Available in Postfix version 2.4 and later:
497 smtp_sasl_tls_verified_security_options ($smtp_sasl_tls_secu‐
499 rity_options)
500 The SASL authentication security options that the Postfix SMTP
501 client uses for TLS encrypted SMTP sessions with a verified
502 server certificate.
503 Available in Postfix version 2.5 and later:
505 smtp_tls_fingerprint_cert_match (empty)
507 List of acceptable remote SMTP server certificate fingerprints
508 for the "fingerprint" TLS security level (smtp_tls_secu‐
509 rity_level = fingerprint).
510 smtp_tls_fingerprint_digest (md5)
512 The message digest algorithm used to construct remote SMTP
513 server certificate fingerprints.
514 Available in Postfix version 2.6 and later:
516 smtp_tls_protocols (!SSLv2, !SSLv3)
518 List of TLS protocols that the Postfix SMTP client will exclude
519 or include with opportunistic TLS encryption.
520 smtp_tls_ciphers (medium)
522 The minimum TLS cipher grade that the Postfix SMTP client will
523 use with opportunistic TLS encryption.
524 smtp_tls_eccert_file (empty)
526 File with the Postfix SMTP client ECDSA certificate in PEM for‐
527 mat.
528 smtp_tls_eckey_file ($smtp_tls_eccert_file)
530 File with the Postfix SMTP client ECDSA private key in PEM for‐
531 mat.
532 Available in Postfix version 2.7 and later:
534 smtp_tls_block_early_mail_reply (no)
536 Try to detect a mail hijacking attack based on a TLS protocol
537 vulnerability (CVE-2009-3555), where an attacker prepends mali‐
538 cious HELO, MAIL, RCPT, DATA commands to a Postfix SMTP client
539 TLS session.
540 Available in Postfix version 2.8 and later:
542 tls_disable_workarounds (see 'postconf -d' output)
544 List or bit-mask of OpenSSL bug work-arounds to disable.
545 Available in Postfix version 2.11-3.1:
547 tls_dane_digest_agility (on)
549 Configure RFC7671 DANE TLSA digest algorithm agility.
550 tls_dane_trust_anchor_digest_enable (yes)
552 Enable support for RFC 6698 (DANE TLSA) DNS records that contain
553 digests of trust-anchors with certificate usage "2".
554 Available in Postfix version 2.11 and later:
556 smtp_tls_trust_anchor_file (empty)
558 Zero or more PEM-format files with trust-anchor certificates
559 and/or public keys.
560 smtp_tls_force_insecure_host_tlsa_lookup (no)
562 Lookup the associated DANE TLSA RRset even when a hostname is
563 not an alias and its address records lie in an unsigned zone.
564 tlsmgr_service_name (tlsmgr)
566 The name of the tlsmgr(8) service entry in master.cf.
567 Available in Postfix version 3.0 and later:
569 smtp_tls_wrappermode (no)
571 Request that the Postfix SMTP client connects using the legacy
572 SMTPS protocol instead of using the STARTTLS command.
573 Available in Postfix version 3.1 and later:
575 smtp_tls_dane_insecure_mx_policy (dane)
577 The TLS policy for MX hosts with "secure" TLSA records when the
578 nexthop destination security level is dane, but the MX record
579 was found via an "insecure" MX lookup.
580 Available in Postfix version 3.4 and later:
582 smtp_tls_connection_reuse (no)
584 Try to make multiple deliveries per TLS-encrypted connection.
585 smtp_tls_chain_files (empty)
587 List of one or more PEM files, each holding one or more private
588 keys directly followed by a corresponding certificate chain.
589 smtp_tls_servername (empty)
591 Optional name to send to the remote SMTP server in the TLS
592 Server Name Indication (SNI) extension.
593
595 The following configuration parameters exist for compatibility with
596 Postfix versions before 2.3. Support for these will be removed in a
597 future release.
598 smtp_use_tls (no)
600 Opportunistic mode: use TLS when a remote SMTP server announces
601 STARTTLS support, otherwise send the mail in the clear.
602 smtp_enforce_tls (no)
604 Enforcement mode: require that remote SMTP servers use TLS
605 encryption, and never send mail in the clear.
606 smtp_tls_enforce_peername (yes)
608 With mandatory TLS encryption, require that the remote SMTP
609 server hostname matches the information in the remote SMTP
610 server certificate.
611 smtp_tls_per_site (empty)
613 Optional lookup tables with the Postfix SMTP client TLS usage
614 policy by next-hop destination and by remote SMTP server host‐
615 name.
616 smtp_tls_cipherlist (empty)
618 Obsolete Postfix < 2.3 control for the Postfix SMTP client TLS
619 cipher list.
620
622 smtp_connect_timeout (30s)
623 The Postfix SMTP client time limit for completing a TCP connec‐
624 tion, or zero (use the operating system built-in time limit).
625 smtp_helo_timeout (300s)
627 The Postfix SMTP client time limit for sending the HELO or EHLO
628 command, and for receiving the initial remote SMTP server
629 response.
630 lmtp_lhlo_timeout (300s)
632 The Postfix LMTP client time limit for sending the LHLO command,
633 and for receiving the initial remote LMTP server response.
634 smtp_xforward_timeout (300s)
636 The Postfix SMTP client time limit for sending the XFORWARD com‐
637 mand, and for receiving the remote SMTP server response.
638 smtp_mail_timeout (300s)
640 The Postfix SMTP client time limit for sending the MAIL FROM
641 command, and for receiving the remote SMTP server response.
642 smtp_rcpt_timeout (300s)
644 The Postfix SMTP client time limit for sending the SMTP RCPT TO
645 command, and for receiving the remote SMTP server response.
646 smtp_data_init_timeout (120s)
648 The Postfix SMTP client time limit for sending the SMTP DATA
649 command, and for receiving the remote SMTP server response.
650 smtp_data_xfer_timeout (180s)
652 The Postfix SMTP client time limit for sending the SMTP message
653 content.
654 smtp_data_done_timeout (600s)
656 The Postfix SMTP client time limit for sending the SMTP ".", and
657 for receiving the remote SMTP server response.
658 smtp_quit_timeout (300s)
660 The Postfix SMTP client time limit for sending the QUIT command,
661 and for receiving the remote SMTP server response.
662 Available in Postfix version 2.1 and later:
664 smtp_mx_address_limit (5)
666 The maximal number of MX (mail exchanger) IP addresses that can
667 result from Postfix SMTP client mail exchanger lookups, or zero
668 (no limit).
669 smtp_mx_session_limit (2)
671 The maximal number of SMTP sessions per delivery request before
672 the Postfix SMTP client gives up or delivers to a fall-back
673 relay host, or zero (no limit).
674 smtp_rset_timeout (20s)
676 The Postfix SMTP client time limit for sending the RSET command,
677 and for receiving the remote SMTP server response.
678 Available in Postfix version 2.2 and earlier:
680 lmtp_cache_connection (yes)
682 Keep Postfix LMTP client connections open for up to $max_idle
683 seconds.
684 Available in Postfix version 2.2 and later:
686 smtp_connection_cache_destinations (empty)
688 Permanently enable SMTP connection caching for the specified
689 destinations.
690 smtp_connection_cache_on_demand (yes)
692 Temporarily enable SMTP connection caching while a destination
693 has a high volume of mail in the active queue.
694 smtp_connection_reuse_time_limit (300s)
696 The amount of time during which Postfix will use an SMTP connec‐
697 tion repeatedly.
698 smtp_connection_cache_time_limit (2s)
700 When SMTP connection caching is enabled, the amount of time that
701 an unused SMTP client socket is kept open before it is closed.
702 Available in Postfix version 2.3 and later:
704 connection_cache_protocol_timeout (5s)
706 Time limit for connection cache connect, send or receive opera‐
707 tions.
708 Available in Postfix version 2.9 and later:
710 smtp_per_record_deadline (no)
712 Change the behavior of the smtp_*_timeout time limits, from a
713 time limit per read or write system call, to a time limit to
714 send or receive a complete record (an SMTP command line, SMTP
715 response line, SMTP message content line, or TLS protocol mes‐
716 sage).
717 Available in Postfix version 2.11 and later:
719 smtp_connection_reuse_count_limit (0)
721 When SMTP connection caching is enabled, the number of times
722 that an SMTP session may be reused before it is closed, or zero
723 (no limit).
724 Available in Postfix version 3.4 and later:
726 smtp_tls_connection_reuse (no)
728 Try to make multiple deliveries per TLS-encrypted connection.
729 Implemented in the qmgr(8) daemon:
731 transport_destination_concurrency_limit ($default_destination_concur‐
733 rency_limit)
734 A transport-specific override for the default_destination_con‐
735 currency_limit parameter value, where transport is the master.cf
736 name of the message delivery transport.
737 transport_destination_recipient_limit ($default_destination_recipi‐
739 ent_limit)
740 A transport-specific override for the default_destination_recip‐
741 ient_limit parameter value, where transport is the master.cf
742 name of the message delivery transport.
743
745 Preliminary SMTPUTF8 support is introduced with Postfix 3.0.
746 smtputf8_enable (yes)
748 Enable preliminary SMTPUTF8 support for the protocols described
749 in RFC 6531..6533.
750 smtputf8_autodetect_classes (sendmail, verify)
752 Detect that a message requires SMTPUTF8 support for the speci‐
753 fied mail origin classes.
754 Available in Postfix version 3.2 and later:
756 enable_idna2003_compatibility (no)
758 Enable 'transitional' compatibility between IDNA2003 and
759 IDNA2008, when converting UTF-8 domain names to/from the ASCII
760 form that is used for DNS lookups.
761
763 debug_peer_level (2)
764 The increment in verbose logging level when a remote client or
765 server matches a pattern in the debug_peer_list parameter.
766 debug_peer_list (empty)
768 Optional list of remote client or server hostname or network
769 address patterns that cause the verbose logging level to
770 increase by the amount specified in $debug_peer_level.
771 error_notice_recipient (postmaster)
773 The recipient of postmaster notifications about mail delivery
774 problems that are caused by policy, resource, software or proto‐
775 col errors.
776 internal_mail_filter_classes (empty)
778 What categories of Postfix-generated mail are subject to
779 before-queue content inspection by non_smtpd_milters,
780 header_checks and body_checks.
781 notify_classes (resource, software)
783 The list of error classes that are reported to the postmaster.
784
786 best_mx_transport (empty)
787 Where the Postfix SMTP client should deliver mail when it
788 detects a "mail loops back to myself" error condition.
789 config_directory (see 'postconf -d' output)
791 The default location of the Postfix main.cf and master.cf con‐
792 figuration files.
793 daemon_timeout (18000s)
795 How much time a Postfix daemon process may take to handle a
796 request before it is terminated by a built-in watchdog timer.
797 delay_logging_resolution_limit (2)
799 The maximal number of digits after the decimal point when log‐
800 ging sub-second delay values.
801 disable_dns_lookups (no)
803 Disable DNS lookups in the Postfix SMTP and LMTP clients.
804 inet_interfaces (all)
806 The network interface addresses that this mail system receives
807 mail on.
808 inet_protocols (all)
810 The Internet protocols Postfix will attempt to use when making
811 or accepting connections.
812 ipc_timeout (3600s)
814 The time limit for sending or receiving information over an
815 internal communication channel.
816 lmtp_assume_final (no)
818 When a remote LMTP server announces no DSN support, assume that
819 the server performs final delivery, and send "delivered" deliv‐
820 ery status notifications instead of "relayed".
821 lmtp_tcp_port (24)
823 The default TCP port that the Postfix LMTP client connects to.
824 max_idle (100s)
826 The maximum amount of time that an idle Postfix daemon process
827 waits for an incoming connection before terminating voluntarily.
828 max_use (100)
830 The maximal number of incoming connections that a Postfix daemon
831 process will service before terminating voluntarily.
832 process_id (read-only)
834 The process ID of a Postfix command or daemon process.
835 process_name (read-only)
837 The process name of a Postfix command or daemon process.
838 proxy_interfaces (empty)
840 The network interface addresses that this mail system receives
841 mail on by way of a proxy or network address translation unit.
842 smtp_address_preference (any)
844 The address type ("ipv6", "ipv4" or "any") that the Postfix SMTP
845 client will try first, when a destination has IPv6 and IPv4
846 addresses with equal MX preference.
847 smtp_bind_address (empty)
849 An optional numerical network address that the Postfix SMTP
850 client should bind to when making an IPv4 connection.
851 smtp_bind_address6 (empty)
853 An optional numerical network address that the Postfix SMTP
854 client should bind to when making an IPv6 connection.
855 smtp_helo_name ($myhostname)
857 The hostname to send in the SMTP HELO or EHLO command.
858 lmtp_lhlo_name ($myhostname)
860 The hostname to send in the LMTP LHLO command.
861 smtp_host_lookup (dns)
863 What mechanisms the Postfix SMTP client uses to look up a host's
864 IP address.
865 smtp_randomize_addresses (yes)
867 Randomize the order of equal-preference MX host addresses.
868 syslog_facility (mail)
870 The syslog facility of Postfix logging.
871 syslog_name (see 'postconf -d' output)
873 A prefix that is prepended to the process name in syslog
874 records, so that, for example, "smtpd" becomes "prefix/smtpd".
875 Available with Postfix 2.2 and earlier:
877 fallback_relay (empty)
879 Optional list of relay hosts for SMTP destinations that can't be
880 found or that are unreachable.
881 Available with Postfix 2.3 and later:
883 smtp_fallback_relay ($fallback_relay)
885 Optional list of relay hosts for SMTP destinations that can't be
886 found or that are unreachable.
887 Available with Postfix 3.0 and later:
889 smtp_address_verify_target (rcpt)
891 In the context of email address verification, the SMTP protocol
892 stage that determines whether an email address is deliverable.
893 Available with Postfix 3.1 and later:
895 lmtp_fallback_relay (empty)
897 Optional list of relay hosts for LMTP destinations that can't be
898 found or that are unreachable.
899 Available with Postfix 3.2 and later:
901 smtp_tcp_port (smtp)
903 The default TCP port that the Postfix SMTP client connects to.
904 Available in Postfix 3.3 and later:
906 service_name (read-only)
908 The master.cf service name of a Postfix daemon process.
909
911 generic(5), output address rewriting
912 header_checks(5), message header content inspection
913 body_checks(5), body parts content inspection
914 qmgr(8), queue manager
915 bounce(8), delivery status reports
916 scache(8), connection cache server
917 postconf(5), configuration parameters
918 master(5), generic daemon options
919 master(8), process manager
920 tlsmgr(8), TLS session and PRNG management
921 postlogd(8), Postfix logging
922 syslogd(8), system logging
923
925 Use "postconf readme_directory" or "postconf html_directory" to locate
926 this information.
927 SASL_README, Postfix SASL howto
928 TLS_README, Postfix STARTTLS howto
929
931 The Secure Mailer license must be distributed with this software.
932
934 Wietse Venema
935 IBM T.J. Watson Research
936 P.O. Box 704
937 Yorktown Heights, NY 10598, USA
938 Wietse Venema
940 Google, Inc.
941 111 8th Avenue
942 New York, NY 10011, USA
943 Command pipelining in cooperation with:
945 Jon Ribbens
946 Oaktree Internet Solutions Ltd.,
947 Internet House,
948 Canal Basin,
949 Coventry,
950 CV1 4LY, United Kingdom.
951 SASL support originally by:
953 Till Franke
954 SuSE Rhein/Main AG
955 65760 Eschborn, Germany
956 TLS support originally by:
958 Lutz Jaenicke
959 BTU Cottbus
960 Allgemeine Elektrotechnik
961 Universitaetsplatz 3-4
962 D-03044 Cottbus, Germany
963 Revised TLS and SMTP connection cache support by:
965 Victor Duchovni
966 Morgan Stanley
967 SMTP(8)