1SMTP(8) System Manager's Manual SMTP(8)
2
6 smtp - Postfix SMTP+LMTP client
7
9 smtp [generic Postfix daemon options] [flags=DORX]
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 The Postfix SMTP+LMTP client supports multiple destinations separated
41 by comma or whitespace (Postfix 3.5 and later). SMTP destinations have
42 the following form:
43 domainname
45 domainname:port
47 Look up the mail exchangers for the specified domain, and con‐
48 nect to the specified port (default: smtp).
49 [hostname]
51 [hostname]:port
53 Look up the address(es) of the specified host, and connect to
54 the specified port (default: smtp).
55 [address]
57 [address]:port
59 Connect to the host at the specified address, and connect to the
60 specified port (default: smtp). An IPv6 address must be format‐
61 ted as [ipv6:address].
62
64 The Postfix SMTP+LMTP client supports multiple destinations separated
65 by comma or whitespace (Postfix 3.5 and later). LMTP destinations have
66 the following form:
67 unix:pathname
69 Connect to the local UNIX-domain server that is bound to the
70 specified pathname. If the process runs chrooted, an absolute
71 pathname is interpreted relative to the Postfix queue directory.
72 inet:hostname
74 inet:hostname:port
76 inet:[address]
78 inet:[address]:port
80 Connect to the specified TCP port on the specified local or re‐
81 mote host. If no port is specified, connect to the port defined
82 as lmtp in services(4). If no such service is found, the
83 lmtp_tcp_port configuration parameter (default value of 24) will
84 be used. An IPv6 address must be formatted as [ipv6:address].
85
87 By default, the Postfix SMTP+LMTP client delivers mail to multiple re‐
88 cipients per delivery request. This is undesirable when prepending a
89 Delivered-to: or X-Original-To: message header. To prevent Postfix from
90 sending multiple recipients per delivery request, specify
91 transport_destination_recipient_limit = 1
93 in the Postfix main.cf file, where transport is the name in the first
95 column of the Postfix master.cf entry for this mail delivery service.
96
98 flags=DORX (optional)
99 Optional message processing flags.
100 D Prepend a "Delivered-To: recipient" message header with
102 the envelope recipient address. Note: for this to work,
103 the transport_destination_recipient_limit must be 1 (see
104 SINGLE-RECIPIENT DELIVERY above for details).
105 The D flag also enforces loop detection: if a message al‐
107 ready contains a Delivered-To: header with the same re‐
108 cipient address, then the message is returned as undeliv‐
109 erable. The address comparison is case insensitive.
110 This feature is available as of Postfix 3.5.
112 O Prepend an "X-Original-To: recipient" message header with
114 the recipient address as given to Postfix. Note: for this
115 to work, the transport_destination_recipient_limit must
116 be 1 (see SINGLE-RECIPIENT DELIVERY above for details).
117 This feature is available as of Postfix 3.5.
119 R Prepend a "Return-Path: <sender>" message header with the
121 envelope sender address.
122 This feature is available as of Postfix 3.5.
124 X Indicates that the delivery is final. This flag affects
126 the status reported in "success" DSN (delivery status no‐
127 tification) messages, and changes it from "relayed" into
128 "delivered".
129 This feature is available as of Postfix 3.5.
131
133 The SMTP+LMTP client is moderately security-sensitive. It
134 talks to SMTP or LMTP servers and to DNS servers on the
135 network. The SMTP+LMTP client can be run chrooted at fixed
136 low privilege.
137
139 RFC 821 (SMTP protocol)
140 RFC 822 (ARPA Internet Text Messages)
141 RFC 1651 (SMTP service extensions)
142 RFC 1652 (8bit-MIME transport)
143 RFC 1870 (Message Size Declaration)
144 RFC 2033 (LMTP protocol)
145 RFC 2034 (SMTP Enhanced Error Codes)
146 RFC 2045 (MIME: Format of Internet Message Bodies)
147 RFC 2046 (MIME: Media Types)
148 RFC 2554 (AUTH command)
149 RFC 2821 (SMTP protocol)
150 RFC 2920 (SMTP Pipelining)
151 RFC 3207 (STARTTLS command)
152 RFC 3461 (SMTP DSN Extension)
153 RFC 3463 (Enhanced Status Codes)
154 RFC 4954 (AUTH command)
155 RFC 5321 (SMTP protocol)
156 RFC 6531 (Internationalized SMTP)
157 RFC 6533 (Internationalized Delivery Status Notifications)
158 RFC 7672 (SMTP security via opportunistic DANE TLS)
159
161 Problems and transactions are logged to syslogd(8) or postlogd(8).
162 Corrupted message files are marked so that the queue manager can move
163 them to the corrupt queue for further inspection.
164 Depending on the setting of the notify_classes parameter, the postmas‐
166 ter is notified of bounces, protocol problems, and of other trouble.
167
169 SMTP and LMTP connection reuse for TLS (without closing the SMTP or
170 LMTP connection) is not supported before Postfix 3.4.
171 SMTP and LMTP connection reuse assumes that SASL credentials are valid
173 for all destinations that map onto the same IP address and TCP port.
174
176 Before Postfix version 2.3, the LMTP client is a separate program that
177 implements only a subset of the functionality available with SMTP:
178 there is no support for TLS, and connections are cached in-process,
179 making it ineffective when the client is used for multiple domains.
180 Most smtp_xxx configuration parameters have an lmtp_xxx "mirror" param‐
182 eter for the equivalent LMTP feature. This document describes only
183 those LMTP-related parameters that aren't simply "mirror" parameters.
184 Changes to main.cf are picked up automatically, as smtp(8) processes
186 run for only a limited amount of time. Use the command "postfix reload"
187 to speed up a change.
188 The text below provides only a parameter summary. See postconf(5) for
190 more details including examples.
191
193 ignore_mx_lookup_error (no)
194 Ignore DNS MX lookups that produce no response.
195 smtp_always_send_ehlo (yes)
197 Always send EHLO at the start of an SMTP session.
198 smtp_never_send_ehlo (no)
200 Never send EHLO at the start of an SMTP session.
201 smtp_defer_if_no_mx_address_found (no)
203 Defer mail delivery when no MX record resolves to an IP address.
204 smtp_line_length_limit (998)
206 The maximal length of message header and body lines that Postfix
207 will send via SMTP.
208 smtp_pix_workaround_delay_time (10s)
210 How long the Postfix SMTP client pauses before sending
211 ".<CR><LF>" in order to work around the PIX firewall
212 "<CR><LF>.<CR><LF>" bug.
213 smtp_pix_workaround_threshold_time (500s)
215 How long a message must be queued before the Postfix SMTP client
216 turns on the PIX firewall "<CR><LF>.<CR><LF>" bug workaround for
217 delivery through firewalls with "smtp fixup" mode turned on.
218 smtp_pix_workarounds (disable_esmtp, delay_dotcrlf)
220 A list that specifies zero or more workarounds for CISCO PIX
221 firewall bugs.
222 smtp_pix_workaround_maps (empty)
224 Lookup tables, indexed by the remote SMTP server address, with
225 per-destination workarounds for CISCO PIX firewall bugs.
226 smtp_quote_rfc821_envelope (yes)
228 Quote addresses in Postfix SMTP client MAIL FROM and RCPT TO
229 commands as required by RFC 5321.
230 smtp_reply_filter (empty)
232 A mechanism to transform replies from remote SMTP servers one
233 line at a time.
234 smtp_skip_5xx_greeting (yes)
236 Skip remote SMTP servers that greet with a 5XX status code.
237 smtp_skip_quit_response (yes)
239 Do not wait for the response to the SMTP QUIT command.
240 Available in Postfix version 2.0 and earlier:
242 smtp_skip_4xx_greeting (yes)
244 Skip SMTP servers that greet with a 4XX status code (go away,
245 try again later).
246 Available in Postfix version 2.2 and later:
248 smtp_discard_ehlo_keyword_address_maps (empty)
250 Lookup tables, indexed by the remote SMTP server address, with
251 case insensitive lists of EHLO keywords (pipelining, starttls,
252 auth, etc.) that the Postfix SMTP client will ignore in the EHLO
253 response from a remote SMTP server.
254 smtp_discard_ehlo_keywords (empty)
256 A case insensitive list of EHLO keywords (pipelining, starttls,
257 auth, etc.) that the Postfix SMTP client will ignore in the EHLO
258 response from a remote SMTP server.
259 smtp_generic_maps (empty)
261 Optional lookup tables that perform address rewriting in the
262 Postfix SMTP client, typically to transform a locally valid ad‐
263 dress into a globally valid address when sending mail across the
264 Internet.
265 Available in Postfix version 2.2.9 and later:
267 smtp_cname_overrides_servername (version dependent)
269 When the remote SMTP servername is a DNS CNAME, replace the
270 servername with the result from CNAME expansion for the purpose
271 of logging, SASL password lookup, TLS policy decisions, or TLS
272 certificate verification.
273 Available in Postfix version 2.3 and later:
275 lmtp_discard_lhlo_keyword_address_maps (empty)
277 Lookup tables, indexed by the remote LMTP server address, with
278 case insensitive lists of LHLO keywords (pipelining, starttls,
279 auth, etc.) that the Postfix LMTP client will ignore in the LHLO
280 response from a remote LMTP server.
281 lmtp_discard_lhlo_keywords (empty)
283 A case insensitive list of LHLO keywords (pipelining, starttls,
284 auth, etc.) that the Postfix LMTP client will ignore in the LHLO
285 response from a remote LMTP server.
286 Available in Postfix version 2.4.4 and later:
288 send_cyrus_sasl_authzid (no)
290 When authenticating to a remote SMTP or LMTP server with the de‐
291 fault setting "no", send no SASL authoriZation ID (authzid);
292 send only the SASL authentiCation ID (authcid) plus the auth‐
293 cid's password.
294 Available in Postfix version 2.5 and later:
296 smtp_header_checks (empty)
298 Restricted header_checks(5) tables for the Postfix SMTP client.
299 smtp_mime_header_checks (empty)
301 Restricted mime_header_checks(5) tables for the Postfix SMTP
302 client.
303 smtp_nested_header_checks (empty)
305 Restricted nested_header_checks(5) tables for the Postfix SMTP
306 client.
307 smtp_body_checks (empty)
309 Restricted body_checks(5) tables for the Postfix SMTP client.
310 Available in Postfix version 2.6 and later:
312 tcp_windowsize (0)
314 An optional workaround for routers that break TCP window scal‐
315 ing.
316 Available in Postfix version 2.8 and later:
318 smtp_dns_resolver_options (empty)
320 DNS Resolver options for the Postfix SMTP client.
321 Available in Postfix version 2.9 and later:
323 smtp_per_record_deadline (no)
325 Change the behavior of the smtp_*_timeout time limits, from a
326 time limit per read or write system call, to a time limit to
327 send or receive a complete record (an SMTP command line, SMTP
328 response line, SMTP message content line, or TLS protocol mes‐
329 sage).
330 smtp_send_dummy_mail_auth (no)
332 Whether or not to append the "AUTH=<>" option to the MAIL FROM
333 command in SASL-authenticated SMTP sessions.
334 Available in Postfix version 2.11 and later:
336 smtp_dns_support_level (empty)
338 Level of DNS support in the Postfix SMTP client.
339 Available in Postfix version 3.0 and later:
341 smtp_delivery_status_filter ($default_delivery_status_filter)
343 Optional filter for the smtp(8) delivery agent to change the de‐
344 livery status code or explanatory text of successful or unsuc‐
345 cessful deliveries.
346 smtp_dns_reply_filter (empty)
348 Optional filter for Postfix SMTP client DNS lookup results.
349 Available in Postfix version 3.3 and later:
351 smtp_balance_inet_protocols (yes)
353 When a remote destination resolves to a combination of IPv4 and
354 IPv6 addresses, ensure that the Postfix SMTP client can try both
355 address types before it runs into the smtp_mx_address_limit.
356 Available in Postfix 3.5 and later:
358 info_log_address_format (external)
360 The email address form that will be used in non-debug logging
361 (info, warning, etc.).
362 Available in Postfix 3.6 and later:
364 dnssec_probe (ns:.)
366 The DNS query type (default: "ns") and DNS query name (default:
367 ".") that Postfix may use to determine whether DNSSEC validation
368 is available.
369 known_tcp_ports (lmtp=24, smtp=25, smtps=submissions=465, submis‐
371 sion=587)
372 Optional setting that avoids lookups in the services(5) data‐
373 base.
374
376 Available in Postfix version 2.0 and later:
377 disable_mime_output_conversion (no)
379 Disable the conversion of 8BITMIME format to 7BIT format.
380 mime_boundary_length_limit (2048)
382 The maximal length of MIME multipart boundary strings.
383 mime_nesting_limit (100)
385 The maximal recursion level that the MIME processor will handle.
386
388 Available in Postfix version 2.1 and later:
389 smtp_send_xforward_command (no)
391 Send the non-standard XFORWARD command when the Postfix SMTP
392 server EHLO response announces XFORWARD support.
393
395 smtp_sasl_auth_enable (no)
396 Enable SASL authentication in the Postfix SMTP client.
397 smtp_sasl_password_maps (empty)
399 Optional Postfix SMTP client lookup tables with one user‐
400 name:password entry per sender, remote hostname or next-hop do‐
401 main.
402 smtp_sasl_security_options (noplaintext, noanonymous)
404 Postfix SMTP client SASL security options; as of Postfix 2.3 the
405 list of available features depends on the SASL client implemen‐
406 tation that is selected with smtp_sasl_type.
407 Available in Postfix version 2.2 and later:
409 smtp_sasl_mechanism_filter (empty)
411 If non-empty, a Postfix SMTP client filter for the remote SMTP
412 server's list of offered SASL mechanisms.
413 Available in Postfix version 2.3 and later:
415 smtp_sender_dependent_authentication (no)
417 Enable sender-dependent authentication in the Postfix SMTP
418 client; this is available only with SASL authentication, and
419 disables SMTP connection caching to ensure that mail from dif‐
420 ferent senders will use the appropriate credentials.
421 smtp_sasl_path (empty)
423 Implementation-specific information that the Postfix SMTP client
424 passes through to the SASL plug-in implementation that is se‐
425 lected with smtp_sasl_type.
426 smtp_sasl_type (cyrus)
428 The SASL plug-in type that the Postfix SMTP client should use
429 for authentication.
430 Available in Postfix version 2.5 and later:
432 smtp_sasl_auth_cache_name (empty)
434 An optional table to prevent repeated SASL authentication fail‐
435 ures with the same remote SMTP server hostname, username and
436 password.
437 smtp_sasl_auth_cache_time (90d)
439 The maximal age of an smtp_sasl_auth_cache_name entry before it
440 is removed.
441 smtp_sasl_auth_soft_bounce (yes)
443 When a remote SMTP server rejects a SASL authentication request
444 with a 535 reply code, defer mail delivery instead of returning
445 mail as undeliverable.
446 Available in Postfix version 2.9 and later:
448 smtp_send_dummy_mail_auth (no)
450 Whether or not to append the "AUTH=<>" option to the MAIL FROM
451 command in SASL-authenticated SMTP sessions.
452
454 Detailed information about STARTTLS configuration may be found in the
455 TLS_README document.
456 smtp_tls_security_level (empty)
458 The default SMTP TLS security level for the Postfix SMTP client;
459 when a non-empty value is specified, this overrides the obsolete
460 parameters smtp_use_tls, smtp_enforce_tls, and smtp_tls_en‐
461 force_peername.
462 smtp_sasl_tls_security_options ($smtp_sasl_security_options)
464 The SASL authentication security options that the Postfix SMTP
465 client uses for TLS encrypted SMTP sessions.
466 smtp_starttls_timeout (300s)
468 Time limit for Postfix SMTP client write and read operations
469 during TLS startup and shutdown handshake procedures.
470 smtp_tls_CAfile (empty)
472 A file containing CA certificates of root CAs trusted to sign
473 either remote SMTP server certificates or intermediate CA cer‐
474 tificates.
475 smtp_tls_CApath (empty)
477 Directory with PEM format Certification Authority certificates
478 that the Postfix SMTP client uses to verify a remote SMTP server
479 certificate.
480 smtp_tls_cert_file (empty)
482 File with the Postfix SMTP client RSA certificate in PEM format.
483 smtp_tls_mandatory_ciphers (medium)
485 The minimum TLS cipher grade that the Postfix SMTP client will
486 use with mandatory TLS encryption.
487 smtp_tls_exclude_ciphers (empty)
489 List of ciphers or cipher types to exclude from the Postfix SMTP
490 client cipher list at all TLS security levels.
491 smtp_tls_mandatory_exclude_ciphers (empty)
493 Additional list of ciphers or cipher types to exclude from the
494 Postfix SMTP client cipher list at mandatory TLS security lev‐
495 els.
496 smtp_tls_dcert_file (empty)
498 File with the Postfix SMTP client DSA certificate in PEM format.
499 smtp_tls_dkey_file ($smtp_tls_dcert_file)
501 File with the Postfix SMTP client DSA private key in PEM format.
502 smtp_tls_key_file ($smtp_tls_cert_file)
504 File with the Postfix SMTP client RSA private key in PEM format.
505 smtp_tls_loglevel (0)
507 Enable additional Postfix SMTP client logging of TLS activity.
508 smtp_tls_note_starttls_offer (no)
510 Log the hostname of a remote SMTP server that offers STARTTLS,
511 when TLS is not already enabled for that server.
512 smtp_tls_policy_maps (empty)
514 Optional lookup tables with the Postfix SMTP client TLS security
515 policy by next-hop destination; when a non-empty value is speci‐
516 fied, this overrides the obsolete smtp_tls_per_site parameter.
517 smtp_tls_mandatory_protocols (see 'postconf -d' output)
519 TLS protocols that the Postfix SMTP client will use with manda‐
520 tory TLS encryption.
521 smtp_tls_scert_verifydepth (9)
523 The verification depth for remote SMTP server certificates.
524 smtp_tls_secure_cert_match (nexthop, dot-nexthop)
526 How the Postfix SMTP client verifies the server certificate
527 peername for the "secure" TLS security level.
528 smtp_tls_session_cache_database (empty)
530 Name of the file containing the optional Postfix SMTP client TLS
531 session cache.
532 smtp_tls_session_cache_timeout (3600s)
534 The expiration time of Postfix SMTP client TLS session cache in‐
535 formation.
536 smtp_tls_verify_cert_match (hostname)
538 How the Postfix SMTP client verifies the server certificate
539 peername for the "verify" TLS security level.
540 tls_daemon_random_bytes (32)
542 The number of pseudo-random bytes that an smtp(8) or smtpd(8)
543 process requests from the tlsmgr(8) server in order to seed its
544 internal pseudo random number generator (PRNG).
545 tls_high_cipherlist (see 'postconf -d' output)
547 The OpenSSL cipherlist for "high" grade ciphers.
548 tls_medium_cipherlist (see 'postconf -d' output)
550 The OpenSSL cipherlist for "medium" or higher grade ciphers.
551 tls_low_cipherlist (see 'postconf -d' output)
553 The OpenSSL cipherlist for "low" or higher grade ciphers.
554 tls_export_cipherlist (see 'postconf -d' output)
556 The OpenSSL cipherlist for "export" or higher grade ciphers.
557 tls_null_cipherlist (eNULL:!aNULL)
559 The OpenSSL cipherlist for "NULL" grade ciphers that provide au‐
560 thentication without encryption.
561 Available in Postfix version 2.4 and later:
563 smtp_sasl_tls_verified_security_options ($smtp_sasl_tls_security_op‐
565 tions)
566 The SASL authentication security options that the Postfix SMTP
567 client uses for TLS encrypted SMTP sessions with a verified
568 server certificate.
569 Available in Postfix version 2.5 and later:
571 smtp_tls_fingerprint_cert_match (empty)
573 List of acceptable remote SMTP server certificate fingerprints
574 for the "fingerprint" TLS security level (smtp_tls_secu‐
575 rity_level = fingerprint).
576 smtp_tls_fingerprint_digest (see 'postconf -d' output)
578 The message digest algorithm used to construct remote SMTP
579 server certificate fingerprints.
580 Available in Postfix version 2.6 and later:
582 smtp_tls_protocols (see postconf -d output)
584 TLS protocols that the Postfix SMTP client will use with oppor‐
585 tunistic TLS encryption.
586 smtp_tls_ciphers (medium)
588 The minimum TLS cipher grade that the Postfix SMTP client will
589 use with opportunistic TLS encryption.
590 smtp_tls_eccert_file (empty)
592 File with the Postfix SMTP client ECDSA certificate in PEM for‐
593 mat.
594 smtp_tls_eckey_file ($smtp_tls_eccert_file)
596 File with the Postfix SMTP client ECDSA private key in PEM for‐
597 mat.
598 Available in Postfix version 2.7 and later:
600 smtp_tls_block_early_mail_reply (no)
602 Try to detect a mail hijacking attack based on a TLS protocol
603 vulnerability (CVE-2009-3555), where an attacker prepends mali‐
604 cious HELO, MAIL, RCPT, DATA commands to a Postfix SMTP client
605 TLS session.
606 Available in Postfix version 2.8 and later:
608 tls_disable_workarounds (see 'postconf -d' output)
610 List or bit-mask of OpenSSL bug work-arounds to disable.
611 Available in Postfix version 2.11-3.1:
613 tls_dane_digest_agility (on)
615 Configure RFC7671 DANE TLSA digest algorithm agility.
616 tls_dane_trust_anchor_digest_enable (yes)
618 Enable support for RFC 6698 (DANE TLSA) DNS records that contain
619 digests of trust-anchors with certificate usage "2".
620 Available in Postfix version 2.11 and later:
622 smtp_tls_trust_anchor_file (empty)
624 Zero or more PEM-format files with trust-anchor certificates
625 and/or public keys.
626 smtp_tls_force_insecure_host_tlsa_lookup (no)
628 Lookup the associated DANE TLSA RRset even when a hostname is
629 not an alias and its address records lie in an unsigned zone.
630 tlsmgr_service_name (tlsmgr)
632 The name of the tlsmgr(8) service entry in master.cf.
633 Available in Postfix version 3.0 and later:
635 smtp_tls_wrappermode (no)
637 Request that the Postfix SMTP client connects using the legacy
638 SMTPS protocol instead of using the STARTTLS command.
639 Available in Postfix version 3.1 and later:
641 smtp_tls_dane_insecure_mx_policy (see 'postconf -d' output)
643 The TLS policy for MX hosts with "secure" TLSA records when the
644 nexthop destination security level is dane, but the MX record
645 was found via an "insecure" MX lookup.
646 Available in Postfix version 3.4 and later:
648 smtp_tls_connection_reuse (no)
650 Try to make multiple deliveries per TLS-encrypted connection.
651 smtp_tls_chain_files (empty)
653 List of one or more PEM files, each holding one or more private
654 keys directly followed by a corresponding certificate chain.
655 smtp_tls_servername (empty)
657 Optional name to send to the remote SMTP server in the TLS
658 Server Name Indication (SNI) extension.
659 Available in Postfix 3.5, 3.4.6, 3.3.5, 3.2.10, 3.1.13 and later:
661 tls_fast_shutdown_enable (yes)
663 A workaround for implementations that hang Postfix while shut‐
664 ting down a TLS session, until Postfix times out.
665
667 The following configuration parameters exist for compatibility with
668 Postfix versions before 2.3. Support for these will be removed in a fu‐
669 ture release.
670 smtp_use_tls (no)
672 Opportunistic mode: use TLS when a remote SMTP server announces
673 STARTTLS support, otherwise send the mail in the clear.
674 smtp_enforce_tls (no)
676 Enforcement mode: require that remote SMTP servers use TLS en‐
677 cryption, and never send mail in the clear.
678 smtp_tls_enforce_peername (yes)
680 With mandatory TLS encryption, require that the remote SMTP
681 server hostname matches the information in the remote SMTP
682 server certificate.
683 smtp_tls_per_site (empty)
685 Optional lookup tables with the Postfix SMTP client TLS usage
686 policy by next-hop destination and by remote SMTP server host‐
687 name.
688 smtp_tls_cipherlist (empty)
690 Obsolete Postfix < 2.3 control for the Postfix SMTP client TLS
691 cipher list.
692
694 smtp_connect_timeout (30s)
695 The Postfix SMTP client time limit for completing a TCP connec‐
696 tion, or zero (use the operating system built-in time limit).
697 smtp_helo_timeout (300s)
699 The Postfix SMTP client time limit for sending the HELO or EHLO
700 command, and for receiving the initial remote SMTP server re‐
701 sponse.
702 lmtp_lhlo_timeout (300s)
704 The Postfix LMTP client time limit for sending the LHLO command,
705 and for receiving the initial remote LMTP server response.
706 smtp_xforward_timeout (300s)
708 The Postfix SMTP client time limit for sending the XFORWARD com‐
709 mand, and for receiving the remote SMTP server response.
710 smtp_mail_timeout (300s)
712 The Postfix SMTP client time limit for sending the MAIL FROM
713 command, and for receiving the remote SMTP server response.
714 smtp_rcpt_timeout (300s)
716 The Postfix SMTP client time limit for sending the SMTP RCPT TO
717 command, and for receiving the remote SMTP server response.
718 smtp_data_init_timeout (120s)
720 The Postfix SMTP client time limit for sending the SMTP DATA
721 command, and for receiving the remote SMTP server response.
722 smtp_data_xfer_timeout (180s)
724 The Postfix SMTP client time limit for sending the SMTP message
725 content.
726 smtp_data_done_timeout (600s)
728 The Postfix SMTP client time limit for sending the SMTP ".", and
729 for receiving the remote SMTP server response.
730 smtp_quit_timeout (300s)
732 The Postfix SMTP client time limit for sending the QUIT command,
733 and for receiving the remote SMTP server response.
734 Available in Postfix version 2.1 and later:
736 smtp_mx_address_limit (5)
738 The maximal number of MX (mail exchanger) IP addresses that can
739 result from Postfix SMTP client mail exchanger lookups, or zero
740 (no limit).
741 smtp_mx_session_limit (2)
743 The maximal number of SMTP sessions per delivery request before
744 the Postfix SMTP client gives up or delivers to a fall-back re‐
745 lay host, or zero (no limit).
746 smtp_rset_timeout (20s)
748 The Postfix SMTP client time limit for sending the RSET command,
749 and for receiving the remote SMTP server response.
750 Available in Postfix version 2.2 and earlier:
752 lmtp_cache_connection (yes)
754 Keep Postfix LMTP client connections open for up to $max_idle
755 seconds.
756 Available in Postfix version 2.2 and later:
758 smtp_connection_cache_destinations (empty)
760 Permanently enable SMTP connection caching for the specified
761 destinations.
762 smtp_connection_cache_on_demand (yes)
764 Temporarily enable SMTP connection caching while a destination
765 has a high volume of mail in the active queue.
766 smtp_connection_reuse_time_limit (300s)
768 The amount of time during which Postfix will use an SMTP connec‐
769 tion repeatedly.
770 smtp_connection_cache_time_limit (2s)
772 When SMTP connection caching is enabled, the amount of time that
773 an unused SMTP client socket is kept open before it is closed.
774 Available in Postfix version 2.3 and later:
776 connection_cache_protocol_timeout (5s)
778 Time limit for connection cache connect, send or receive opera‐
779 tions.
780 Available in Postfix version 2.9 and later:
782 smtp_per_record_deadline (no)
784 Change the behavior of the smtp_*_timeout time limits, from a
785 time limit per read or write system call, to a time limit to
786 send or receive a complete record (an SMTP command line, SMTP
787 response line, SMTP message content line, or TLS protocol mes‐
788 sage).
789 Available in Postfix version 2.11 and later:
791 smtp_connection_reuse_count_limit (0)
793 When SMTP connection caching is enabled, the number of times
794 that an SMTP session may be reused before it is closed, or zero
795 (no limit).
796 Available in Postfix version 3.4 and later:
798 smtp_tls_connection_reuse (no)
800 Try to make multiple deliveries per TLS-encrypted connection.
801 Implemented in the qmgr(8) daemon:
803 transport_destination_concurrency_limit ($default_destination_concur‐
805 rency_limit)
806 A transport-specific override for the default_destination_con‐
807 currency_limit parameter value, where transport is the master.cf
808 name of the message delivery transport.
809 transport_destination_recipient_limit ($default_destination_recipi‐
811 ent_limit)
812 A transport-specific override for the default_destination_recip‐
813 ient_limit parameter value, where transport is the master.cf
814 name of the message delivery transport.
815
817 Preliminary SMTPUTF8 support is introduced with Postfix 3.0.
818 smtputf8_enable (yes)
820 Enable preliminary SMTPUTF8 support for the protocols described
821 in RFC 6531..6533.
822 smtputf8_autodetect_classes (sendmail, verify)
824 Detect that a message requires SMTPUTF8 support for the speci‐
825 fied mail origin classes.
826 Available in Postfix version 3.2 and later:
828 enable_idna2003_compatibility (no)
830 Enable 'transitional' compatibility between IDNA2003 and
831 IDNA2008, when converting UTF-8 domain names to/from the ASCII
832 form that is used for DNS lookups.
833
835 debug_peer_level (2)
836 The increment in verbose logging level when a nexthop destina‐
837 tion, remote client or server name or network address matches a
838 pattern given with the debug_peer_list parameter.
839 debug_peer_list (empty)
841 Optional list of nexthop destination, remote client or server
842 name or network address patterns that, if matched, cause the
843 verbose logging level to increase by the amount specified in
844 $debug_peer_level.
845 error_notice_recipient (postmaster)
847 The recipient of postmaster notifications about mail delivery
848 problems that are caused by policy, resource, software or proto‐
849 col errors.
850 internal_mail_filter_classes (empty)
852 What categories of Postfix-generated mail are subject to be‐
853 fore-queue content inspection by non_smtpd_milters,
854 header_checks and body_checks.
855 notify_classes (resource, software)
857 The list of error classes that are reported to the postmaster.
858
860 best_mx_transport (empty)
861 Where the Postfix SMTP client should deliver mail when it de‐
862 tects a "mail loops back to myself" error condition.
863 config_directory (see 'postconf -d' output)
865 The default location of the Postfix main.cf and master.cf con‐
866 figuration files.
867 daemon_timeout (18000s)
869 How much time a Postfix daemon process may take to handle a re‐
870 quest before it is terminated by a built-in watchdog timer.
871 delay_logging_resolution_limit (2)
873 The maximal number of digits after the decimal point when log‐
874 ging sub-second delay values.
875 disable_dns_lookups (no)
877 Disable DNS lookups in the Postfix SMTP and LMTP clients.
878 inet_interfaces (all)
880 The network interface addresses that this mail system receives
881 mail on.
882 inet_protocols (see 'postconf -d output')
884 The Internet protocols Postfix will attempt to use when making
885 or accepting connections.
886 ipc_timeout (3600s)
888 The time limit for sending or receiving information over an in‐
889 ternal communication channel.
890 lmtp_assume_final (no)
892 When a remote LMTP server announces no DSN support, assume that
893 the server performs final delivery, and send "delivered" deliv‐
894 ery status notifications instead of "relayed".
895 lmtp_tcp_port (24)
897 The default TCP port that the Postfix LMTP client connects to.
898 max_idle (100s)
900 The maximum amount of time that an idle Postfix daemon process
901 waits for an incoming connection before terminating voluntarily.
902 max_use (100)
904 The maximal number of incoming connections that a Postfix daemon
905 process will service before terminating voluntarily.
906 process_id (read-only)
908 The process ID of a Postfix command or daemon process.
909 process_name (read-only)
911 The process name of a Postfix command or daemon process.
912 proxy_interfaces (empty)
914 The network interface addresses that this mail system receives
915 mail on by way of a proxy or network address translation unit.
916 smtp_address_preference (any)
918 The address type ("ipv6", "ipv4" or "any") that the Postfix SMTP
919 client will try first, when a destination has IPv6 and IPv4 ad‐
920 dresses with equal MX preference.
921 smtp_bind_address (empty)
923 An optional numerical network address that the Postfix SMTP
924 client should bind to when making an IPv4 connection.
925 smtp_bind_address6 (empty)
927 An optional numerical network address that the Postfix SMTP
928 client should bind to when making an IPv6 connection.
929 smtp_helo_name ($myhostname)
931 The hostname to send in the SMTP HELO or EHLO command.
932 lmtp_lhlo_name ($myhostname)
934 The hostname to send in the LMTP LHLO command.
935 smtp_host_lookup (dns)
937 What mechanisms the Postfix SMTP client uses to look up a host's
938 IP address.
939 smtp_randomize_addresses (yes)
941 Randomize the order of equal-preference MX host addresses.
942 syslog_facility (mail)
944 The syslog facility of Postfix logging.
945 syslog_name (see 'postconf -d' output)
947 A prefix that is prepended to the process name in syslog
948 records, so that, for example, "smtpd" becomes "prefix/smtpd".
949 Available with Postfix 2.2 and earlier:
951 fallback_relay (empty)
953 Optional list of relay hosts for SMTP destinations that can't be
954 found or that are unreachable.
955 Available with Postfix 2.3 and later:
957 smtp_fallback_relay ($fallback_relay)
959 Optional list of relay hosts for SMTP destinations that can't be
960 found or that are unreachable.
961 Available with Postfix 3.0 and later:
963 smtp_address_verify_target (rcpt)
965 In the context of email address verification, the SMTP protocol
966 stage that determines whether an email address is deliverable.
967 Available with Postfix 3.1 and later:
969 lmtp_fallback_relay (empty)
971 Optional list of relay hosts for LMTP destinations that can't be
972 found or that are unreachable.
973 Available with Postfix 3.2 and later:
975 smtp_tcp_port (smtp)
977 The default TCP port that the Postfix SMTP client connects to.
978 Available in Postfix 3.3 and later:
980 service_name (read-only)
982 The master.cf service name of a Postfix daemon process.
983
985 generic(5), output address rewriting
986 header_checks(5), message header content inspection
987 body_checks(5), body parts content inspection
988 qmgr(8), queue manager
989 bounce(8), delivery status reports
990 scache(8), connection cache server
991 postconf(5), configuration parameters
992 master(5), generic daemon options
993 master(8), process manager
994 tlsmgr(8), TLS session and PRNG management
995 postlogd(8), Postfix logging
996 syslogd(8), system logging
997
999 Use "postconf readme_directory" or "postconf html_directory" to locate
1000 this information.
1001 SASL_README, Postfix SASL howto
1002 TLS_README, Postfix STARTTLS howto
1003
1005 The Secure Mailer license must be distributed with this software.
1006
1008 Wietse Venema
1009 IBM T.J. Watson Research
1010 P.O. Box 704
1011 Yorktown Heights, NY 10598, USA
1012 Wietse Venema
1014 Google, Inc.
1015 111 8th Avenue
1016 New York, NY 10011, USA
1017 Command pipelining in cooperation with:
1019 Jon Ribbens
1020 Oaktree Internet Solutions Ltd.,
1021 Internet House,
1022 Canal Basin,
1023 Coventry,
1024 CV1 4LY, United Kingdom.
1025 SASL support originally by:
1027 Till Franke
1028 SuSE Rhein/Main AG
1029 65760 Eschborn, Germany
1030 TLS support originally by:
1032 Lutz Jaenicke
1033 BTU Cottbus
1034 Allgemeine Elektrotechnik
1035 Universitaetsplatz 3-4
1036 D-03044 Cottbus, Germany
1037 Revised TLS and SMTP connection cache support by:
1039 Victor Duchovni
1040 Morgan Stanley
1041 SMTP(8)