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 reuse for TLS (without closing the SMTP or
120 LMTP connection) is not supported before Postfix 3.4.
121 SMTP and LMTP connection caching assumes that SASL credentials are
123 valid for all destinations that map onto the same IP address and TCP
124 port.
125
127 Before Postfix version 2.3, the LMTP client is a separate program that
128 implements only a subset of the functionality available with SMTP:
129 there is no support for TLS, and connections are cached in-process,
130 making it ineffective when the client is used for multiple domains.
131 Most smtp_xxx configuration parameters have an lmtp_xxx "mirror" param‐
133 eter for the equivalent LMTP feature. This document describes only
134 those LMTP-related parameters that aren't simply "mirror" parameters.
135 Changes to main.cf are picked up automatically, as smtp(8) processes
137 run for only a limited amount of time. Use the command "postfix reload"
138 to speed up a change.
139 The text below provides only a parameter summary. See postconf(5) for
141 more details including examples.
142
144 ignore_mx_lookup_error (no)
145 Ignore DNS MX lookups that produce no response.
146 smtp_always_send_ehlo (yes)
148 Always send EHLO at the start of an SMTP session.
149 smtp_never_send_ehlo (no)
151 Never send EHLO at the start of an SMTP session.
152 smtp_defer_if_no_mx_address_found (no)
154 Defer mail delivery when no MX record resolves to an IP address.
155 smtp_line_length_limit (998)
157 The maximal length of message header and body lines that Postfix
158 will send via SMTP.
159 smtp_pix_workaround_delay_time (10s)
161 How long the Postfix SMTP client pauses before sending
162 ".<CR><LF>" in order to work around the PIX firewall
163 "<CR><LF>.<CR><LF>" bug.
164 smtp_pix_workaround_threshold_time (500s)
166 How long a message must be queued before the Postfix SMTP client
167 turns on the PIX firewall "<CR><LF>.<CR><LF>" bug workaround for
168 delivery through firewalls with "smtp fixup" mode turned on.
169 smtp_pix_workarounds (disable_esmtp, delay_dotcrlf)
171 A list that specifies zero or more workarounds for CISCO PIX
172 firewall bugs.
173 smtp_pix_workaround_maps (empty)
175 Lookup tables, indexed by the remote SMTP server address, with
176 per-destination workarounds for CISCO PIX firewall bugs.
177 smtp_quote_rfc821_envelope (yes)
179 Quote addresses in Postfix SMTP client MAIL FROM and RCPT TO
180 commands as required by RFC 5321.
181 smtp_reply_filter (empty)
183 A mechanism to transform replies from remote SMTP servers one
184 line at a time.
185 smtp_skip_5xx_greeting (yes)
187 Skip remote SMTP servers that greet with a 5XX status code.
188 smtp_skip_quit_response (yes)
190 Do not wait for the response to the SMTP QUIT command.
191 Available in Postfix version 2.0 and earlier:
193 smtp_skip_4xx_greeting (yes)
195 Skip SMTP servers that greet with a 4XX status code (go away,
196 try again later).
197 Available in Postfix version 2.2 and later:
199 smtp_discard_ehlo_keyword_address_maps (empty)
201 Lookup tables, indexed by the remote SMTP server address, with
202 case insensitive lists of EHLO keywords (pipelining, starttls,
203 auth, etc.) that the Postfix SMTP client will ignore in the EHLO
204 response from a remote SMTP server.
205 smtp_discard_ehlo_keywords (empty)
207 A case insensitive list of EHLO keywords (pipelining, starttls,
208 auth, etc.) that the Postfix SMTP client will ignore in the EHLO
209 response from a remote SMTP server.
210 smtp_generic_maps (empty)
212 Optional lookup tables that perform address rewriting in the
213 Postfix SMTP client, typically to transform a locally valid
214 address into a globally valid address when sending mail across
215 the Internet.
216 Available in Postfix version 2.2.9 and later:
218 smtp_cname_overrides_servername (version dependent)
220 When the remote SMTP servername is a DNS CNAME, replace the
221 servername with the result from CNAME expansion for the purpose
222 of logging, SASL password lookup, TLS policy decisions, or TLS
223 certificate verification.
224 Available in Postfix version 2.3 and later:
226 lmtp_discard_lhlo_keyword_address_maps (empty)
228 Lookup tables, indexed by the remote LMTP server address, with
229 case insensitive lists of LHLO keywords (pipelining, starttls,
230 auth, etc.) that the Postfix LMTP client will ignore in the LHLO
231 response from a remote LMTP server.
232 lmtp_discard_lhlo_keywords (empty)
234 A case insensitive list of LHLO keywords (pipelining, starttls,
235 auth, etc.) that the Postfix LMTP client will ignore in the LHLO
236 response from a remote LMTP server.
237 Available in Postfix version 2.4.4 and later:
239 send_cyrus_sasl_authzid (no)
241 When authenticating to a remote SMTP or LMTP server with the
242 default setting "no", send no SASL authoriZation ID (authzid);
243 send only the SASL authentiCation ID (authcid) plus the auth‐
244 cid's password.
245 Available in Postfix version 2.5 and later:
247 smtp_header_checks (empty)
249 Restricted header_checks(5) tables for the Postfix SMTP client.
250 smtp_mime_header_checks (empty)
252 Restricted mime_header_checks(5) tables for the Postfix SMTP
253 client.
254 smtp_nested_header_checks (empty)
256 Restricted nested_header_checks(5) tables for the Postfix SMTP
257 client.
258 smtp_body_checks (empty)
260 Restricted body_checks(5) tables for the Postfix SMTP client.
261 Available in Postfix version 2.6 and later:
263 tcp_windowsize (0)
265 An optional workaround for routers that break TCP window scal‐
266 ing.
267 Available in Postfix version 2.8 and later:
269 smtp_dns_resolver_options (empty)
271 DNS Resolver options for the Postfix SMTP client.
272 Available in Postfix version 2.9 and later:
274 smtp_per_record_deadline (no)
276 Change the behavior of the smtp_*_timeout time limits, from a
277 time limit per read or write system call, to a time limit to
278 send or receive a complete record (an SMTP command line, SMTP
279 response line, SMTP message content line, or TLS protocol mes‐
280 sage).
281 smtp_send_dummy_mail_auth (no)
283 Whether or not to append the "AUTH=<>" option to the MAIL FROM
284 command in SASL-authenticated SMTP sessions.
285 Available in Postfix version 2.11 and later:
287 smtp_dns_support_level (empty)
289 Level of DNS support in the Postfix SMTP client.
290 Available in Postfix version 3.0 and later:
292 smtp_delivery_status_filter ($default_delivery_status_filter)
294 Optional filter for the smtp(8) delivery agent to change the
295 delivery status code or explanatory text of successful or unsuc‐
296 cessful deliveries.
297 smtp_dns_reply_filter (empty)
299 Optional filter for Postfix SMTP client DNS lookup results.
300 Available in Postfix version 3.3 and later:
302 smtp_balance_inet_protocols (yes)
304 When a remote destination resolves to a combination of IPv4 and
305 IPv6 addresses, ensure that the Postfix SMTP client can try both
306 address types before it runs into the smtp_mx_address_limit.
307
309 Available in Postfix version 2.0 and later:
310 disable_mime_output_conversion (no)
312 Disable the conversion of 8BITMIME format to 7BIT format.
313 mime_boundary_length_limit (2048)
315 The maximal length of MIME multipart boundary strings.
316 mime_nesting_limit (100)
318 The maximal recursion level that the MIME processor will handle.
319
321 Available in Postfix version 2.1 and later:
322 smtp_send_xforward_command (no)
324 Send the non-standard XFORWARD command when the Postfix SMTP
325 server EHLO response announces XFORWARD support.
326
328 smtp_sasl_auth_enable (no)
329 Enable SASL authentication in the Postfix SMTP client.
330 smtp_sasl_password_maps (empty)
332 Optional Postfix SMTP client lookup tables with one user‐
333 name:password entry per sender, remote hostname or next-hop
334 domain.
335 smtp_sasl_security_options (noplaintext, noanonymous)
337 Postfix SMTP client SASL security options; as of Postfix 2.3 the
338 list of available features depends on the SASL client implemen‐
339 tation that is selected with smtp_sasl_type.
340 Available in Postfix version 2.2 and later:
342 smtp_sasl_mechanism_filter (empty)
344 If non-empty, a Postfix SMTP client filter for the remote SMTP
345 server's list of offered SASL mechanisms.
346 Available in Postfix version 2.3 and later:
348 smtp_sender_dependent_authentication (no)
350 Enable sender-dependent authentication in the Postfix SMTP
351 client; this is available only with SASL authentication, and
352 disables SMTP connection caching to ensure that mail from dif‐
353 ferent senders will use the appropriate credentials.
354 smtp_sasl_path (empty)
356 Implementation-specific information that the Postfix SMTP client
357 passes through to the SASL plug-in implementation that is
358 selected with smtp_sasl_type.
359 smtp_sasl_type (cyrus)
361 The SASL plug-in type that the Postfix SMTP client should use
362 for authentication.
363 Available in Postfix version 2.5 and later:
365 smtp_sasl_auth_cache_name (empty)
367 An optional table to prevent repeated SASL authentication fail‐
368 ures with the same remote SMTP server hostname, username and
369 password.
370 smtp_sasl_auth_cache_time (90d)
372 The maximal age of an smtp_sasl_auth_cache_name entry before it
373 is removed.
374 smtp_sasl_auth_soft_bounce (yes)
376 When a remote SMTP server rejects a SASL authentication request
377 with a 535 reply code, defer mail delivery instead of returning
378 mail as undeliverable.
379 Available in Postfix version 2.9 and later:
381 smtp_send_dummy_mail_auth (no)
383 Whether or not to append the "AUTH=<>" option to the MAIL FROM
384 command in SASL-authenticated SMTP sessions.
385
387 Detailed information about STARTTLS configuration may be found in the
388 TLS_README document.
389 smtp_tls_security_level (empty)
391 The default SMTP TLS security level for the Postfix SMTP client;
392 when a non-empty value is specified, this overrides the obsolete
393 parameters smtp_use_tls, smtp_enforce_tls, and
394 smtp_tls_enforce_peername.
395 smtp_sasl_tls_security_options ($smtp_sasl_security_options)
397 The SASL authentication security options that the Postfix SMTP
398 client uses for TLS encrypted SMTP sessions.
399 smtp_starttls_timeout (300s)
401 Time limit for Postfix SMTP client write and read operations
402 during TLS startup and shutdown handshake procedures.
403 smtp_tls_CAfile (empty)
405 A file containing CA certificates of root CAs trusted to sign
406 either remote SMTP server certificates or intermediate CA cer‐
407 tificates.
408 smtp_tls_CApath (empty)
410 Directory with PEM format Certification Authority certificates
411 that the Postfix SMTP client uses to verify a remote SMTP server
412 certificate.
413 smtp_tls_cert_file (empty)
415 File with the Postfix SMTP client RSA certificate in PEM format.
416 smtp_tls_mandatory_ciphers (medium)
418 The minimum TLS cipher grade that the Postfix SMTP client will
419 use with mandatory TLS encryption.
420 smtp_tls_exclude_ciphers (empty)
422 List of ciphers or cipher types to exclude from the Postfix SMTP
423 client cipher list at all TLS security levels.
424 smtp_tls_mandatory_exclude_ciphers (empty)
426 Additional list of ciphers or cipher types to exclude from the
427 Postfix SMTP client cipher list at mandatory TLS security lev‐
428 els.
429 smtp_tls_dcert_file (empty)
431 File with the Postfix SMTP client DSA certificate in PEM format.
432 smtp_tls_dkey_file ($smtp_tls_dcert_file)
434 File with the Postfix SMTP client DSA private key in PEM format.
435 smtp_tls_key_file ($smtp_tls_cert_file)
437 File with the Postfix SMTP client RSA private key in PEM format.
438 smtp_tls_loglevel (0)
440 Enable additional Postfix SMTP client logging of TLS activity.
441 smtp_tls_note_starttls_offer (no)
443 Log the hostname of a remote SMTP server that offers STARTTLS,
444 when TLS is not already enabled for that server.
445 smtp_tls_policy_maps (empty)
447 Optional lookup tables with the Postfix SMTP client TLS security
448 policy by next-hop destination; when a non-empty value is speci‐
449 fied, this overrides the obsolete smtp_tls_per_site parameter.
450 smtp_tls_mandatory_protocols (!SSLv2, !SSLv3)
452 List of SSL/TLS protocols that the Postfix SMTP client will use
453 with mandatory TLS encryption.
454 smtp_tls_scert_verifydepth (9)
456 The verification depth for remote SMTP server certificates.
457 smtp_tls_secure_cert_match (nexthop, dot-nexthop)
459 How the Postfix SMTP client verifies the server certificate
460 peername for the "secure" TLS security level.
461 smtp_tls_session_cache_database (empty)
463 Name of the file containing the optional Postfix SMTP client TLS
464 session cache.
465 smtp_tls_session_cache_timeout (3600s)
467 The expiration time of Postfix SMTP client TLS session cache
468 information.
469 smtp_tls_verify_cert_match (hostname)
471 How the Postfix SMTP client verifies the server certificate
472 peername for the "verify" TLS security level.
473 tls_daemon_random_bytes (32)
475 The number of pseudo-random bytes that an smtp(8) or smtpd(8)
476 process requests from the tlsmgr(8) server in order to seed its
477 internal pseudo random number generator (PRNG).
478 tls_high_cipherlist (see 'postconf -d' output)
480 The OpenSSL cipherlist for "high" grade ciphers.
481 tls_medium_cipherlist (see 'postconf -d' output)
483 The OpenSSL cipherlist for "medium" or higher grade ciphers.
484 tls_low_cipherlist (see 'postconf -d' output)
486 The OpenSSL cipherlist for "low" or higher grade ciphers.
487 tls_export_cipherlist (see 'postconf -d' output)
489 The OpenSSL cipherlist for "export" or higher grade ciphers.
490 tls_null_cipherlist (eNULL:!aNULL)
492 The OpenSSL cipherlist for "NULL" grade ciphers that provide
493 authentication without encryption.
494 Available in Postfix version 2.4 and later:
496 smtp_sasl_tls_verified_security_options ($smtp_sasl_tls_secu‐
498 rity_options)
499 The SASL authentication security options that the Postfix SMTP
500 client uses for TLS encrypted SMTP sessions with a verified
501 server certificate.
502 Available in Postfix version 2.5 and later:
504 smtp_tls_fingerprint_cert_match (empty)
506 List of acceptable remote SMTP server certificate fingerprints
507 for the "fingerprint" TLS security level (smtp_tls_secu‐
508 rity_level = fingerprint).
509 smtp_tls_fingerprint_digest (md5)
511 The message digest algorithm used to construct remote SMTP
512 server certificate fingerprints.
513 Available in Postfix version 2.6 and later:
515 smtp_tls_protocols (!SSLv2, !SSLv3)
517 List of TLS protocols that the Postfix SMTP client will exclude
518 or include with opportunistic TLS encryption.
519 smtp_tls_ciphers (medium)
521 The minimum TLS cipher grade that the Postfix SMTP client will
522 use with opportunistic TLS encryption.
523 smtp_tls_eccert_file (empty)
525 File with the Postfix SMTP client ECDSA certificate in PEM for‐
526 mat.
527 smtp_tls_eckey_file ($smtp_tls_eccert_file)
529 File with the Postfix SMTP client ECDSA private key in PEM for‐
530 mat.
531 Available in Postfix version 2.7 and later:
533 smtp_tls_block_early_mail_reply (no)
535 Try to detect a mail hijacking attack based on a TLS protocol
536 vulnerability (CVE-2009-3555), where an attacker prepends mali‐
537 cious HELO, MAIL, RCPT, DATA commands to a Postfix SMTP client
538 TLS session.
539 Available in Postfix version 2.8 and later:
541 tls_disable_workarounds (see 'postconf -d' output)
543 List or bit-mask of OpenSSL bug work-arounds to disable.
544 Available in Postfix version 2.11-3.1:
546 tls_dane_digest_agility (on)
548 Configure RFC7671 DANE TLSA digest algorithm agility.
549 tls_dane_trust_anchor_digest_enable (yes)
551 Enable support for RFC 6698 (DANE TLSA) DNS records that contain
552 digests of trust-anchors with certificate usage "2".
553 Available in Postfix version 2.11 and later:
555 smtp_tls_trust_anchor_file (empty)
557 Zero or more PEM-format files with trust-anchor certificates
558 and/or public keys.
559 smtp_tls_force_insecure_host_tlsa_lookup (no)
561 Lookup the associated DANE TLSA RRset even when a hostname is
562 not an alias and its address records lie in an unsigned zone.
563 tlsmgr_service_name (tlsmgr)
565 The name of the tlsmgr(8) service entry in master.cf.
566 Available in Postfix version 3.0 and later:
568 smtp_tls_wrappermode (no)
570 Request that the Postfix SMTP client connects using the legacy
571 SMTPS protocol instead of using the STARTTLS command.
572 Available in Postfix version 3.1 and later:
574 smtp_tls_dane_insecure_mx_policy (dane)
576 The TLS policy for MX hosts with "secure" TLSA records when the
577 nexthop destination security level is dane, but the MX record
578 was found via an "insecure" MX lookup.
579 Available in Postfix version 3.4 and later:
581 smtp_tls_connection_reuse (no)
583 Try to make multiple deliveries per TLS-encrypted connection.
584 smtp_tls_chain_files (empty)
586 List of one or more PEM files, each holding one or more private
587 keys directly followed by a corresponding certificate chain.
588 smtp_tls_servername (empty)
590 Optional name to send to the remote SMTP server in the TLS
591 Server Name Indication (SNI) extension.
592 Introduced with Postfix 3.4.6, 3.3.5, 3.2.10, and 3.1.13:
594 tls_fast_shutdown_enable (yes)
596 A workaround for implementations that hang Postfix while shuting
597 down a TLS session, until Postfix times out.
598
600 The following configuration parameters exist for compatibility with
601 Postfix versions before 2.3. Support for these will be removed in a
602 future release.
603 smtp_use_tls (no)
605 Opportunistic mode: use TLS when a remote SMTP server announces
606 STARTTLS support, otherwise send the mail in the clear.
607 smtp_enforce_tls (no)
609 Enforcement mode: require that remote SMTP servers use TLS
610 encryption, and never send mail in the clear.
611 smtp_tls_enforce_peername (yes)
613 With mandatory TLS encryption, require that the remote SMTP
614 server hostname matches the information in the remote SMTP
615 server certificate.
616 smtp_tls_per_site (empty)
618 Optional lookup tables with the Postfix SMTP client TLS usage
619 policy by next-hop destination and by remote SMTP server host‐
620 name.
621 smtp_tls_cipherlist (empty)
623 Obsolete Postfix < 2.3 control for the Postfix SMTP client TLS
624 cipher list.
625
627 smtp_connect_timeout (30s)
628 The Postfix SMTP client time limit for completing a TCP connec‐
629 tion, or zero (use the operating system built-in time limit).
630 smtp_helo_timeout (300s)
632 The Postfix SMTP client time limit for sending the HELO or EHLO
633 command, and for receiving the initial remote SMTP server
634 response.
635 lmtp_lhlo_timeout (300s)
637 The Postfix LMTP client time limit for sending the LHLO command,
638 and for receiving the initial remote LMTP server response.
639 smtp_xforward_timeout (300s)
641 The Postfix SMTP client time limit for sending the XFORWARD com‐
642 mand, and for receiving the remote SMTP server response.
643 smtp_mail_timeout (300s)
645 The Postfix SMTP client time limit for sending the MAIL FROM
646 command, and for receiving the remote SMTP server response.
647 smtp_rcpt_timeout (300s)
649 The Postfix SMTP client time limit for sending the SMTP RCPT TO
650 command, and for receiving the remote SMTP server response.
651 smtp_data_init_timeout (120s)
653 The Postfix SMTP client time limit for sending the SMTP DATA
654 command, and for receiving the remote SMTP server response.
655 smtp_data_xfer_timeout (180s)
657 The Postfix SMTP client time limit for sending the SMTP message
658 content.
659 smtp_data_done_timeout (600s)
661 The Postfix SMTP client time limit for sending the SMTP ".", and
662 for receiving the remote SMTP server response.
663 smtp_quit_timeout (300s)
665 The Postfix SMTP client time limit for sending the QUIT command,
666 and for receiving the remote SMTP server response.
667 Available in Postfix version 2.1 and later:
669 smtp_mx_address_limit (5)
671 The maximal number of MX (mail exchanger) IP addresses that can
672 result from Postfix SMTP client mail exchanger lookups, or zero
673 (no limit).
674 smtp_mx_session_limit (2)
676 The maximal number of SMTP sessions per delivery request before
677 the Postfix SMTP client gives up or delivers to a fall-back
678 relay host, or zero (no limit).
679 smtp_rset_timeout (20s)
681 The Postfix SMTP client time limit for sending the RSET command,
682 and for receiving the remote SMTP server response.
683 Available in Postfix version 2.2 and earlier:
685 lmtp_cache_connection (yes)
687 Keep Postfix LMTP client connections open for up to $max_idle
688 seconds.
689 Available in Postfix version 2.2 and later:
691 smtp_connection_cache_destinations (empty)
693 Permanently enable SMTP connection caching for the specified
694 destinations.
695 smtp_connection_cache_on_demand (yes)
697 Temporarily enable SMTP connection caching while a destination
698 has a high volume of mail in the active queue.
699 smtp_connection_reuse_time_limit (300s)
701 The amount of time during which Postfix will use an SMTP connec‐
702 tion repeatedly.
703 smtp_connection_cache_time_limit (2s)
705 When SMTP connection caching is enabled, the amount of time that
706 an unused SMTP client socket is kept open before it is closed.
707 Available in Postfix version 2.3 and later:
709 connection_cache_protocol_timeout (5s)
711 Time limit for connection cache connect, send or receive opera‐
712 tions.
713 Available in Postfix version 2.9 and later:
715 smtp_per_record_deadline (no)
717 Change the behavior of the smtp_*_timeout time limits, from a
718 time limit per read or write system call, to a time limit to
719 send or receive a complete record (an SMTP command line, SMTP
720 response line, SMTP message content line, or TLS protocol mes‐
721 sage).
722 Available in Postfix version 2.11 and later:
724 smtp_connection_reuse_count_limit (0)
726 When SMTP connection caching is enabled, the number of times
727 that an SMTP session may be reused before it is closed, or zero
728 (no limit).
729 Available in Postfix version 3.4 and later:
731 smtp_tls_connection_reuse (no)
733 Try to make multiple deliveries per TLS-encrypted connection.
734 Implemented in the qmgr(8) daemon:
736 transport_destination_concurrency_limit ($default_destination_concur‐
738 rency_limit)
739 A transport-specific override for the default_destination_con‐
740 currency_limit parameter value, where transport is the master.cf
741 name of the message delivery transport.
742 transport_destination_recipient_limit ($default_destination_recipi‐
744 ent_limit)
745 A transport-specific override for the default_destination_recip‐
746 ient_limit parameter value, where transport is the master.cf
747 name of the message delivery transport.
748
750 Preliminary SMTPUTF8 support is introduced with Postfix 3.0.
751 smtputf8_enable (yes)
753 Enable preliminary SMTPUTF8 support for the protocols described
754 in RFC 6531..6533.
755 smtputf8_autodetect_classes (sendmail, verify)
757 Detect that a message requires SMTPUTF8 support for the speci‐
758 fied mail origin classes.
759 Available in Postfix version 3.2 and later:
761 enable_idna2003_compatibility (no)
763 Enable 'transitional' compatibility between IDNA2003 and
764 IDNA2008, when converting UTF-8 domain names to/from the ASCII
765 form that is used for DNS lookups.
766
768 debug_peer_level (2)
769 The increment in verbose logging level when a remote client or
770 server matches a pattern in the debug_peer_list parameter.
771 debug_peer_list (empty)
773 Optional list of remote client or server hostname or network
774 address patterns that cause the verbose logging level to
775 increase by the amount specified in $debug_peer_level.
776 error_notice_recipient (postmaster)
778 The recipient of postmaster notifications about mail delivery
779 problems that are caused by policy, resource, software or proto‐
780 col errors.
781 internal_mail_filter_classes (empty)
783 What categories of Postfix-generated mail are subject to
784 before-queue content inspection by non_smtpd_milters,
785 header_checks and body_checks.
786 notify_classes (resource, software)
788 The list of error classes that are reported to the postmaster.
789
791 best_mx_transport (empty)
792 Where the Postfix SMTP client should deliver mail when it
793 detects a "mail loops back to myself" error condition.
794 config_directory (see 'postconf -d' output)
796 The default location of the Postfix main.cf and master.cf con‐
797 figuration files.
798 daemon_timeout (18000s)
800 How much time a Postfix daemon process may take to handle a
801 request before it is terminated by a built-in watchdog timer.
802 delay_logging_resolution_limit (2)
804 The maximal number of digits after the decimal point when log‐
805 ging sub-second delay values.
806 disable_dns_lookups (no)
808 Disable DNS lookups in the Postfix SMTP and LMTP clients.
809 inet_interfaces (all)
811 The network interface addresses that this mail system receives
812 mail on.
813 inet_protocols (all)
815 The Internet protocols Postfix will attempt to use when making
816 or accepting connections.
817 ipc_timeout (3600s)
819 The time limit for sending or receiving information over an
820 internal communication channel.
821 lmtp_assume_final (no)
823 When a remote LMTP server announces no DSN support, assume that
824 the server performs final delivery, and send "delivered" deliv‐
825 ery status notifications instead of "relayed".
826 lmtp_tcp_port (24)
828 The default TCP port that the Postfix LMTP client connects to.
829 max_idle (100s)
831 The maximum amount of time that an idle Postfix daemon process
832 waits for an incoming connection before terminating voluntarily.
833 max_use (100)
835 The maximal number of incoming connections that a Postfix daemon
836 process will service before terminating voluntarily.
837 process_id (read-only)
839 The process ID of a Postfix command or daemon process.
840 process_name (read-only)
842 The process name of a Postfix command or daemon process.
843 proxy_interfaces (empty)
845 The network interface addresses that this mail system receives
846 mail on by way of a proxy or network address translation unit.
847 smtp_address_preference (any)
849 The address type ("ipv6", "ipv4" or "any") that the Postfix SMTP
850 client will try first, when a destination has IPv6 and IPv4
851 addresses with equal MX preference.
852 smtp_bind_address (empty)
854 An optional numerical network address that the Postfix SMTP
855 client should bind to when making an IPv4 connection.
856 smtp_bind_address6 (empty)
858 An optional numerical network address that the Postfix SMTP
859 client should bind to when making an IPv6 connection.
860 smtp_helo_name ($myhostname)
862 The hostname to send in the SMTP HELO or EHLO command.
863 lmtp_lhlo_name ($myhostname)
865 The hostname to send in the LMTP LHLO command.
866 smtp_host_lookup (dns)
868 What mechanisms the Postfix SMTP client uses to look up a host's
869 IP address.
870 smtp_randomize_addresses (yes)
872 Randomize the order of equal-preference MX host addresses.
873 syslog_facility (mail)
875 The syslog facility of Postfix logging.
876 syslog_name (see 'postconf -d' output)
878 A prefix that is prepended to the process name in syslog
879 records, so that, for example, "smtpd" becomes "prefix/smtpd".
880 Available with Postfix 2.2 and earlier:
882 fallback_relay (empty)
884 Optional list of relay hosts for SMTP destinations that can't be
885 found or that are unreachable.
886 Available with Postfix 2.3 and later:
888 smtp_fallback_relay ($fallback_relay)
890 Optional list of relay hosts for SMTP destinations that can't be
891 found or that are unreachable.
892 Available with Postfix 3.0 and later:
894 smtp_address_verify_target (rcpt)
896 In the context of email address verification, the SMTP protocol
897 stage that determines whether an email address is deliverable.
898 Available with Postfix 3.1 and later:
900 lmtp_fallback_relay (empty)
902 Optional list of relay hosts for LMTP destinations that can't be
903 found or that are unreachable.
904 Available with Postfix 3.2 and later:
906 smtp_tcp_port (smtp)
908 The default TCP port that the Postfix SMTP client connects to.
909 Available in Postfix 3.3 and later:
911 service_name (read-only)
913 The master.cf service name of a Postfix daemon process.
914
916 generic(5), output address rewriting
917 header_checks(5), message header content inspection
918 body_checks(5), body parts content inspection
919 qmgr(8), queue manager
920 bounce(8), delivery status reports
921 scache(8), connection cache server
922 postconf(5), configuration parameters
923 master(5), generic daemon options
924 master(8), process manager
925 tlsmgr(8), TLS session and PRNG management
926 postlogd(8), Postfix logging
927 syslogd(8), system logging
928
930 Use "postconf readme_directory" or "postconf html_directory" to locate
931 this information.
932 SASL_README, Postfix SASL howto
933 TLS_README, Postfix STARTTLS howto
934
936 The Secure Mailer license must be distributed with this software.
937
939 Wietse Venema
940 IBM T.J. Watson Research
941 P.O. Box 704
942 Yorktown Heights, NY 10598, USA
943 Wietse Venema
945 Google, Inc.
946 111 8th Avenue
947 New York, NY 10011, USA
948 Command pipelining in cooperation with:
950 Jon Ribbens
951 Oaktree Internet Solutions Ltd.,
952 Internet House,
953 Canal Basin,
954 Coventry,
955 CV1 4LY, United Kingdom.
956 SASL support originally by:
958 Till Franke
959 SuSE Rhein/Main AG
960 65760 Eschborn, Germany
961 TLS support originally by:
963 Lutz Jaenicke
964 BTU Cottbus
965 Allgemeine Elektrotechnik
966 Universitaetsplatz 3-4
967 D-03044 Cottbus, Germany
968 Revised TLS and SMTP connection cache support by:
970 Victor Duchovni
971 Morgan Stanley
972 SMTP(8)