1SMTPD(8) System Manager's Manual SMTPD(8)
2
6 smtpd - Postfix SMTP server
7
9 smtpd [generic Postfix daemon options]
10 sendmail -bs
12
14 The SMTP server accepts network connection requests and performs zero
15 or more SMTP transactions per connection. Each received message is
16 piped through the cleanup(8) daemon, and is placed into the incoming
17 queue as one single queue file. For this mode of operation, the pro‐
18 gram expects to be run from the master(8) process manager.
19 Alternatively, the SMTP server be can run in stand-alone mode; this is
21 traditionally obtained with "sendmail -bs". When the SMTP server runs
22 stand-alone with non $mail_owner privileges, it receives mail even
23 while the mail system is not running, deposits messages directly into
24 the maildrop queue, and disables the SMTP server's access policies. As
25 of Postfix version 2.3, the SMTP server refuses to receive mail from
26 the network when it runs with non $mail_owner privileges.
27 The SMTP server implements a variety of policies for connection
29 requests, and for parameters given to HELO, ETRN, MAIL FROM, VRFY and
30 RCPT TO commands. They are detailed below and in the main.cf configura‐
31 tion file.
32
34 The SMTP server is moderately security-sensitive. It talks to SMTP
35 clients and to DNS servers on the network. The SMTP server can be run
36 chrooted at fixed low privilege.
37
39 RFC 821 (SMTP protocol)
40 RFC 1123 (Host requirements)
41 RFC 1652 (8bit-MIME transport)
42 RFC 1869 (SMTP service extensions)
43 RFC 1870 (Message size declaration)
44 RFC 1985 (ETRN command)
45 RFC 2034 (SMTP enhanced status codes)
46 RFC 2554 (AUTH command)
47 RFC 2821 (SMTP protocol)
48 RFC 2920 (SMTP pipelining)
49 RFC 3030 (CHUNKING without BINARYMIME)
50 RFC 3207 (STARTTLS command)
51 RFC 3461 (SMTP DSN extension)
52 RFC 3463 (Enhanced status codes)
53 RFC 3848 (ESMTP transmission types)
54 RFC 4409 (Message submission)
55 RFC 4954 (AUTH command)
56 RFC 5321 (SMTP protocol)
57 RFC 6531 (Internationalized SMTP)
58 RFC 6533 (Internationalized Delivery Status Notifications)
59 RFC 7505 ("Null MX" No Service Resource Record)
60
62 Problems and transactions are logged to syslogd(8) or postlogd(8).
63 Depending on the setting of the notify_classes parameter, the postmas‐
65 ter is notified of bounces, protocol problems, policy violations, and
66 of other trouble.
67
69 Changes to main.cf are picked up automatically, as smtpd(8) processes
70 run for only a limited amount of time. Use the command "postfix reload"
71 to speed up a change.
72 The text below provides only a parameter summary. See postconf(5) for
74 more details including examples.
75
77 The following parameters work around implementation errors in other
78 software, and/or allow you to override standards in order to prevent
79 undesirable use.
80 broken_sasl_auth_clients (no)
82 Enable interoperability with remote SMTP clients that implement
83 an obsolete version of the AUTH command (RFC 4954).
84 disable_vrfy_command (no)
86 Disable the SMTP VRFY command.
87 smtpd_noop_commands (empty)
89 List of commands that the Postfix SMTP server replies to with
90 "250 Ok", without doing any syntax checks and without changing
91 state.
92 strict_rfc821_envelopes (no)
94 Require that addresses received in SMTP MAIL FROM and RCPT TO
95 commands are enclosed with <>, and that those addresses do not
96 contain RFC 822 style comments or phrases.
97 Available in Postfix version 2.1 and later:
99 smtpd_reject_unlisted_sender (no)
101 Request that the Postfix SMTP server rejects mail from unknown
102 sender addresses, even when no explicit reject_unlisted_sender
103 access restriction is specified.
104 smtpd_sasl_exceptions_networks (empty)
106 What remote SMTP clients the Postfix SMTP server will not offer
107 AUTH support to.
108 Available in Postfix version 2.2 and later:
110 smtpd_discard_ehlo_keyword_address_maps (empty)
112 Lookup tables, indexed by the remote SMTP client address, with
113 case insensitive lists of EHLO keywords (pipelining, starttls,
114 auth, etc.) that the Postfix SMTP server will not send in the
115 EHLO response to a remote SMTP client.
116 smtpd_discard_ehlo_keywords (empty)
118 A case insensitive list of EHLO keywords (pipelining, starttls,
119 auth, etc.) that the Postfix SMTP server will not send in the
120 EHLO response to a remote SMTP client.
121 smtpd_delay_open_until_valid_rcpt (yes)
123 Postpone the start of an SMTP mail transaction until a valid
124 RCPT TO command is received.
125 Available in Postfix version 2.3 and later:
127 smtpd_tls_always_issue_session_ids (yes)
129 Force the Postfix SMTP server to issue a TLS session id, even
130 when TLS session caching is turned off (smtpd_tls_ses‐
131 sion_cache_database is empty).
132 Available in Postfix version 2.6 and later:
134 tcp_windowsize (0)
136 An optional workaround for routers that break TCP window scal‐
137 ing.
138 Available in Postfix version 2.7 and later:
140 smtpd_command_filter (empty)
142 A mechanism to transform commands from remote SMTP clients.
143 Available in Postfix version 2.9 and later:
145 smtpd_per_record_deadline (normal: no, overload: yes)
147 Change the behavior of the smtpd_timeout and smtpd_start‐
148 tls_timeout time limits, from a time limit per read or write
149 system call, to a time limit to send or receive a complete
150 record (an SMTP command line, SMTP response line, SMTP message
151 content line, or TLS protocol message).
152 Available in Postfix version 3.0 and later:
154 smtpd_dns_reply_filter (empty)
156 Optional filter for Postfix SMTP server DNS lookup results.
157
159 See the ADDRESS_REWRITING_README document for a detailed discussion of
160 Postfix address rewriting.
161 receive_override_options (empty)
163 Enable or disable recipient validation, built-in content filter‐
164 ing, or address mapping.
165 Available in Postfix version 2.2 and later:
167 local_header_rewrite_clients (permit_inet_interfaces)
169 Rewrite message header addresses in mail from these clients and
170 update incomplete addresses with the domain name in $myorigin or
171 $mydomain; either don't rewrite message headers from other
172 clients at all, or rewrite message headers and update incomplete
173 addresses with the domain specified in the remote_header_re‐
174 write_domain parameter.
175
177 Available in Postfix version 2.10 and later:
178 smtpd_upstream_proxy_protocol (empty)
180 The name of the proxy protocol used by an optional before-smtpd
181 proxy agent.
182 smtpd_upstream_proxy_timeout (5s)
184 The time limit for the proxy protocol specified with the
185 smtpd_upstream_proxy_protocol parameter.
186
188 As of version 1.0, Postfix can be configured to send new mail to an
189 external content filter AFTER the mail is queued. This content filter
190 is expected to inject mail back into a (Postfix or other) MTA for fur‐
191 ther delivery. See the FILTER_README document for details.
192 content_filter (empty)
194 After the message is queued, send the entire message to the
195 specified transport:destination.
196
198 As of version 2.1, the Postfix SMTP server can be configured to send
199 incoming mail to a real-time SMTP-based content filter BEFORE mail is
200 queued. This content filter is expected to inject mail back into Post‐
201 fix. See the SMTPD_PROXY_README document for details on how to config‐
202 ure and operate this feature.
203 smtpd_proxy_filter (empty)
205 The hostname and TCP port of the mail filtering proxy server.
206 smtpd_proxy_ehlo ($myhostname)
208 How the Postfix SMTP server announces itself to the proxy fil‐
209 ter.
210 smtpd_proxy_options (empty)
212 List of options that control how the Postfix SMTP server commu‐
213 nicates with a before-queue content filter.
214 smtpd_proxy_timeout (100s)
216 The time limit for connecting to a proxy filter and for sending
217 or receiving information.
218
220 As of version 2.3, Postfix supports the Sendmail version 8 Milter (mail
221 filter) protocol. These content filters run outside Postfix. They can
222 inspect the SMTP command stream and the message content, and can
223 request modifications before mail is queued. For details see the MIL‐
224 TER_README document.
225 smtpd_milters (empty)
227 A list of Milter (mail filter) applications for new mail that
228 arrives via the Postfix smtpd(8) server.
229 milter_protocol (6)
231 The mail filter protocol version and optional protocol exten‐
232 sions for communication with a Milter application; prior to
233 Postfix 2.6 the default protocol is 2.
234 milter_default_action (tempfail)
236 The default action when a Milter (mail filter) application is
237 unavailable or mis-configured.
238 milter_macro_daemon_name ($myhostname)
240 The {daemon_name} macro value for Milter (mail filter) applica‐
241 tions.
242 milter_macro_v ($mail_name $mail_version)
244 The {v} macro value for Milter (mail filter) applications.
245 milter_connect_timeout (30s)
247 The time limit for connecting to a Milter (mail filter) applica‐
248 tion, and for negotiating protocol options.
249 milter_command_timeout (30s)
251 The time limit for sending an SMTP command to a Milter (mail
252 filter) application, and for receiving the response.
253 milter_content_timeout (300s)
255 The time limit for sending message content to a Milter (mail
256 filter) application, and for receiving the response.
257 milter_connect_macros (see 'postconf -d' output)
259 The macros that are sent to Milter (mail filter) applications
260 after completion of an SMTP connection.
261 milter_helo_macros (see 'postconf -d' output)
263 The macros that are sent to Milter (mail filter) applications
264 after the SMTP HELO or EHLO command.
265 milter_mail_macros (see 'postconf -d' output)
267 The macros that are sent to Milter (mail filter) applications
268 after the SMTP MAIL FROM command.
269 milter_rcpt_macros (see 'postconf -d' output)
271 The macros that are sent to Milter (mail filter) applications
272 after the SMTP RCPT TO command.
273 milter_data_macros (see 'postconf -d' output)
275 The macros that are sent to version 4 or higher Milter (mail
276 filter) applications after the SMTP DATA command.
277 milter_unknown_command_macros (see 'postconf -d' output)
279 The macros that are sent to version 3 or higher Milter (mail
280 filter) applications after an unknown SMTP command.
281 milter_end_of_header_macros (see 'postconf -d' output)
283 The macros that are sent to Milter (mail filter) applications
284 after the end of the message header.
285 milter_end_of_data_macros (see 'postconf -d' output)
287 The macros that are sent to Milter (mail filter) applications
288 after the message end-of-data.
289 Available in Postfix version 3.1 and later:
291 milter_macro_defaults (empty)
293 Optional list of name=value pairs that specify default values
294 for arbitrary macros that Postfix may send to Milter applica‐
295 tions.
296 Available in Postfix version 3.2 and later:
298 smtpd_milter_maps (empty)
300 Lookup tables with Milter settings per remote SMTP client IP
301 address.
302
304 The following parameters are applicable for both built-in and external
305 content filters.
306 Available in Postfix version 2.1 and later:
308 receive_override_options (empty)
310 Enable or disable recipient validation, built-in content filter‐
311 ing, or address mapping.
312
314 The following parameters are applicable for both before-queue and
315 after-queue content filtering.
316 Available in Postfix version 2.1 and later:
318 smtpd_authorized_xforward_hosts (empty)
320 What remote SMTP clients are allowed to use the XFORWARD fea‐
321 ture.
322
324 Postfix SASL support (RFC 4954) can be used to authenticate remote SMTP
325 clients to the Postfix SMTP server, and to authenticate the Postfix
326 SMTP client to a remote SMTP server. See the SASL_README document for
327 details.
328 broken_sasl_auth_clients (no)
330 Enable interoperability with remote SMTP clients that implement
331 an obsolete version of the AUTH command (RFC 4954).
332 smtpd_sasl_auth_enable (no)
334 Enable SASL authentication in the Postfix SMTP server.
335 smtpd_sasl_local_domain (empty)
337 The name of the Postfix SMTP server's local SASL authentication
338 realm.
339 smtpd_sasl_security_options (noanonymous)
341 Postfix SMTP server SASL security options; as of Postfix 2.3 the
342 list of available features depends on the SASL server implemen‐
343 tation that is selected with smtpd_sasl_type.
344 smtpd_sender_login_maps (empty)
346 Optional lookup table with the SASL login names that own the
347 sender (MAIL FROM) addresses.
348 Available in Postfix version 2.1 and later:
350 smtpd_sasl_exceptions_networks (empty)
352 What remote SMTP clients the Postfix SMTP server will not offer
353 AUTH support to.
354 Available in Postfix version 2.1 and 2.2:
356 smtpd_sasl_application_name (smtpd)
358 The application name that the Postfix SMTP server uses for SASL
359 server initialization.
360 Available in Postfix version 2.3 and later:
362 smtpd_sasl_authenticated_header (no)
364 Report the SASL authenticated user name in the smtpd(8) Received
365 message header.
366 smtpd_sasl_path (smtpd)
368 Implementation-specific information that the Postfix SMTP server
369 passes through to the SASL plug-in implementation that is
370 selected with smtpd_sasl_type.
371 smtpd_sasl_type (cyrus)
373 The SASL plug-in type that the Postfix SMTP server should use
374 for authentication.
375 Available in Postfix version 2.5 and later:
377 cyrus_sasl_config_path (empty)
379 Search path for Cyrus SASL application configuration files, cur‐
380 rently used only to locate the $smtpd_sasl_path.conf file.
381 Available in Postfix version 2.11 and later:
383 smtpd_sasl_service (smtp)
385 The service name that is passed to the SASL plug-in that is
386 selected with smtpd_sasl_type and smtpd_sasl_path.
387 Available in Postfix version 3.4 and later:
389 smtpd_sasl_response_limit (12288)
391 The maximum length of a SASL client's response to a server chal‐
392 lenge.
393
395 Detailed information about STARTTLS configuration may be found in the
396 TLS_README document.
397 smtpd_tls_security_level (empty)
399 The SMTP TLS security level for the Postfix SMTP server; when a
400 non-empty value is specified, this overrides the obsolete param‐
401 eters smtpd_use_tls and smtpd_enforce_tls.
402 smtpd_sasl_tls_security_options ($smtpd_sasl_security_options)
404 The SASL authentication security options that the Postfix SMTP
405 server uses for TLS encrypted SMTP sessions.
406 smtpd_starttls_timeout (see 'postconf -d' output)
408 The time limit for Postfix SMTP server write and read operations
409 during TLS startup and shutdown handshake procedures.
410 smtpd_tls_CAfile (empty)
412 A file containing (PEM format) CA certificates of root CAs
413 trusted to sign either remote SMTP client certificates or inter‐
414 mediate CA certificates.
415 smtpd_tls_CApath (empty)
417 A directory containing (PEM format) CA certificates of root CAs
418 trusted to sign either remote SMTP client certificates or inter‐
419 mediate CA certificates.
420 smtpd_tls_always_issue_session_ids (yes)
422 Force the Postfix SMTP server to issue a TLS session id, even
423 when TLS session caching is turned off (smtpd_tls_ses‐
424 sion_cache_database is empty).
425 smtpd_tls_ask_ccert (no)
427 Ask a remote SMTP client for a client certificate.
428 smtpd_tls_auth_only (no)
430 When TLS encryption is optional in the Postfix SMTP server, do
431 not announce or accept SASL authentication over unencrypted con‐
432 nections.
433 smtpd_tls_ccert_verifydepth (9)
435 The verification depth for remote SMTP client certificates.
436 smtpd_tls_cert_file (empty)
438 File with the Postfix SMTP server RSA certificate in PEM format.
439 smtpd_tls_exclude_ciphers (empty)
441 List of ciphers or cipher types to exclude from the SMTP server
442 cipher list at all TLS security levels.
443 smtpd_tls_dcert_file (empty)
445 File with the Postfix SMTP server DSA certificate in PEM format.
446 smtpd_tls_dh1024_param_file (empty)
448 File with DH parameters that the Postfix SMTP server should use
449 with non-export EDH ciphers.
450 smtpd_tls_dh512_param_file (empty)
452 File with DH parameters that the Postfix SMTP server should use
453 with export-grade EDH ciphers.
454 smtpd_tls_dkey_file ($smtpd_tls_dcert_file)
456 File with the Postfix SMTP server DSA private key in PEM format.
457 smtpd_tls_key_file ($smtpd_tls_cert_file)
459 File with the Postfix SMTP server RSA private key in PEM format.
460 smtpd_tls_loglevel (0)
462 Enable additional Postfix SMTP server logging of TLS activity.
463 smtpd_tls_mandatory_ciphers (medium)
465 The minimum TLS cipher grade that the Postfix SMTP server will
466 use with mandatory TLS encryption.
467 smtpd_tls_mandatory_exclude_ciphers (empty)
469 Additional list of ciphers or cipher types to exclude from the
470 Postfix SMTP server cipher list at mandatory TLS security lev‐
471 els.
472 smtpd_tls_mandatory_protocols (!SSLv2, !SSLv3)
474 The SSL/TLS protocols accepted by the Postfix SMTP server with
475 mandatory TLS encryption.
476 smtpd_tls_received_header (no)
478 Request that the Postfix SMTP server produces Received: message
479 headers that include information about the protocol and cipher
480 used, as well as the remote SMTP client CommonName and client
481 certificate issuer CommonName.
482 smtpd_tls_req_ccert (no)
484 With mandatory TLS encryption, require a trusted remote SMTP
485 client certificate in order to allow TLS connections to proceed.
486 smtpd_tls_wrappermode (no)
488 Run the Postfix SMTP server in the non-standard "wrapper" mode,
489 instead of using the STARTTLS command.
490 tls_daemon_random_bytes (32)
492 The number of pseudo-random bytes that an smtp(8) or smtpd(8)
493 process requests from the tlsmgr(8) server in order to seed its
494 internal pseudo random number generator (PRNG).
495 tls_high_cipherlist (see 'postconf -d' output)
497 The OpenSSL cipherlist for "high" grade ciphers.
498 tls_medium_cipherlist (see 'postconf -d' output)
500 The OpenSSL cipherlist for "medium" or higher grade ciphers.
501 tls_low_cipherlist (see 'postconf -d' output)
503 The OpenSSL cipherlist for "low" or higher grade ciphers.
504 tls_export_cipherlist (see 'postconf -d' output)
506 The OpenSSL cipherlist for "export" or higher grade ciphers.
507 tls_null_cipherlist (eNULL:!aNULL)
509 The OpenSSL cipherlist for "NULL" grade ciphers that provide
510 authentication without encryption.
511 Available in Postfix version 2.5 and later:
513 smtpd_tls_fingerprint_digest (md5)
515 The message digest algorithm to construct remote SMTP
516 client-certificate fingerprints or public key fingerprints
517 (Postfix 2.9 and later) for check_ccert_access and per‐
518 mit_tls_clientcerts.
519 Available in Postfix version 2.6 and later:
521 smtpd_tls_protocols (!SSLv2, !SSLv3)
523 List of TLS protocols that the Postfix SMTP server will exclude
524 or include with opportunistic TLS encryption.
525 smtpd_tls_ciphers (medium)
527 The minimum TLS cipher grade that the Postfix SMTP server will
528 use with opportunistic TLS encryption.
529 smtpd_tls_eccert_file (empty)
531 File with the Postfix SMTP server ECDSA certificate in PEM for‐
532 mat.
533 smtpd_tls_eckey_file ($smtpd_tls_eccert_file)
535 File with the Postfix SMTP server ECDSA private key in PEM for‐
536 mat.
537 smtpd_tls_eecdh_grade (see 'postconf -d' output)
539 The Postfix SMTP server security grade for ephemeral ellip‐
540 tic-curve Diffie-Hellman (EECDH) key exchange.
541 tls_eecdh_strong_curve (prime256v1)
543 The elliptic curve used by the Postfix SMTP server for sensibly
544 strong ephemeral ECDH key exchange.
545 tls_eecdh_ultra_curve (secp384r1)
547 The elliptic curve used by the Postfix SMTP server for maximally
548 strong ephemeral ECDH key exchange.
549 Available in Postfix version 2.8 and later:
551 tls_preempt_cipherlist (no)
553 With SSLv3 and later, use the Postfix SMTP server's cipher pref‐
554 erence order instead of the remote client's cipher preference
555 order.
556 tls_disable_workarounds (see 'postconf -d' output)
558 List or bit-mask of OpenSSL bug work-arounds to disable.
559 Available in Postfix version 2.11 and later:
561 tlsmgr_service_name (tlsmgr)
563 The name of the tlsmgr(8) service entry in master.cf.
564 Available in Postfix version 3.0 and later:
566 tls_session_ticket_cipher (Postfix >= 3.0: aes-256-cbc, Postfix < 3.0:
568 aes-128-cbc)
569 Algorithm used to encrypt RFC5077 TLS session tickets.
570 Available in Postfix version 3.2 and later:
572 tls_eecdh_auto_curves (see 'postconf -d' output)
574 The prioritized list of elliptic curves supported by the Postfix
575 SMTP client and server.
576 Available in Postfix version 3.4 and later:
578 smtpd_tls_chain_files (empty)
580 List of one or more PEM files, each holding one or more private
581 keys directly followed by a corresponding certificate chain.
582 tls_server_sni_maps (empty)
584 Optional lookup tables that map names received from remote SMTP
585 clients via the TLS Server Name Indication (SNI) extension to
586 the appropriate keys and certificate chains.
587 Introduced with Postfix 3.4.6, 3.3.5, 3.2.10, and 3.1.13:
589 tls_fast_shutdown_enable (yes)
591 A workaround for implementations that hang Postfix while shuting
592 down a TLS session, until Postfix times out.
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 smtpd_use_tls (no)
600 Opportunistic TLS: announce STARTTLS support to remote SMTP
601 clients, but do not require that clients use TLS encryption.
602 smtpd_enforce_tls (no)
604 Mandatory TLS: announce STARTTLS support to remote SMTP clients,
605 and require that clients use TLS encryption.
606 smtpd_tls_cipherlist (empty)
608 Obsolete Postfix < 2.3 control for the Postfix SMTP server TLS
609 cipher list.
610
612 Preliminary SMTPUTF8 support is introduced with Postfix 3.0.
613 smtputf8_enable (yes)
615 Enable preliminary SMTPUTF8 support for the protocols described
616 in RFC 6531..6533.
617 strict_smtputf8 (no)
619 Enable stricter enforcement of the SMTPUTF8 protocol.
620 smtputf8_autodetect_classes (sendmail, verify)
622 Detect that a message requires SMTPUTF8 support for the speci‐
623 fied mail origin classes.
624 Available in Postfix version 3.2 and later:
626 enable_idna2003_compatibility (no)
628 Enable 'transitional' compatibility between IDNA2003 and
629 IDNA2008, when converting UTF-8 domain names to/from the ASCII
630 form that is used for DNS lookups.
631
633 With VERP style delivery, each recipient of a message receives a cus‐
634 tomized copy of the message with his/her own recipient address encoded
635 in the envelope sender address. The VERP_README file describes config‐
636 uration and operation details of Postfix support for variable envelope
637 return path addresses. VERP style delivery is requested with the SMTP
638 XVERP command or with the "sendmail -V" command-line option and is
639 available in Postfix version 1.1 and later.
640 default_verp_delimiters (+=)
642 The two default VERP delimiter characters.
643 verp_delimiter_filter (-=+)
645 The characters Postfix accepts as VERP delimiter characters on
646 the Postfix sendmail(1) command line and in SMTP commands.
647 Available in Postfix version 1.1 and 2.0:
649 authorized_verp_clients ($mynetworks)
651 What remote SMTP clients are allowed to specify the XVERP com‐
652 mand.
653 Available in Postfix version 2.1 and later:
655 smtpd_authorized_verp_clients ($authorized_verp_clients)
657 What remote SMTP clients are allowed to specify the XVERP com‐
658 mand.
659
661 The DEBUG_README document describes how to debug parts of the Postfix
662 mail system. The methods vary from making the software log a lot of
663 detail, to running some daemon processes under control of a call tracer
664 or debugger.
665 debug_peer_level (2)
667 The increment in verbose logging level when a remote client or
668 server matches a pattern in the debug_peer_list parameter.
669 debug_peer_list (empty)
671 Optional list of remote client or server hostname or network
672 address patterns that cause the verbose logging level to
673 increase by the amount specified in $debug_peer_level.
674 error_notice_recipient (postmaster)
676 The recipient of postmaster notifications about mail delivery
677 problems that are caused by policy, resource, software or proto‐
678 col errors.
679 internal_mail_filter_classes (empty)
681 What categories of Postfix-generated mail are subject to
682 before-queue content inspection by non_smtpd_milters,
683 header_checks and body_checks.
684 notify_classes (resource, software)
686 The list of error classes that are reported to the postmaster.
687 smtpd_reject_footer (empty)
689 Optional information that is appended after each Postfix SMTP
690 server 4XX or 5XX response.
691 soft_bounce (no)
693 Safety net to keep mail queued that would otherwise be returned
694 to the sender.
695 Available in Postfix version 2.1 and later:
697 smtpd_authorized_xclient_hosts (empty)
699 What remote SMTP clients are allowed to use the XCLIENT feature.
700 Available in Postfix version 2.10 and later:
702 smtpd_log_access_permit_actions (empty)
704 Enable logging of the named "permit" actions in SMTP server
705 access lists (by default, the SMTP server logs "reject" actions
706 but not "permit" actions).
707
709 As of Postfix version 2.0, the SMTP server rejects mail for unknown
710 recipients. This prevents the mail queue from clogging up with undeliv‐
711 erable MAILER-DAEMON messages. Additional information on this topic is
712 in the LOCAL_RECIPIENT_README and ADDRESS_CLASS_README documents.
713 show_user_unknown_table_name (yes)
715 Display the name of the recipient table in the "User unknown"
716 responses.
717 canonical_maps (empty)
719 Optional address mapping lookup tables for message headers and
720 envelopes.
721 recipient_canonical_maps (empty)
723 Optional address mapping lookup tables for envelope and header
724 recipient addresses.
725 sender_canonical_maps (empty)
727 Optional address mapping lookup tables for envelope and header
728 sender addresses.
729 Parameters concerning known/unknown local recipients:
731 mydestination ($myhostname, localhost.$mydomain, localhost)
733 The list of domains that are delivered via the $local_transport
734 mail delivery transport.
735 inet_interfaces (all)
737 The network interface addresses that this mail system receives
738 mail on.
739 proxy_interfaces (empty)
741 The network interface addresses that this mail system receives
742 mail on by way of a proxy or network address translation unit.
743 inet_protocols (all)
745 The Internet protocols Postfix will attempt to use when making
746 or accepting connections.
747 local_recipient_maps (proxy:unix:passwd.byname $alias_maps)
749 Lookup tables with all names or addresses of local recipients: a
750 recipient address is local when its domain matches $mydestina‐
751 tion, $inet_interfaces or $proxy_interfaces.
752 unknown_local_recipient_reject_code (550)
754 The numerical Postfix SMTP server response code when a recipient
755 address is local, and $local_recipient_maps specifies a list of
756 lookup tables that does not match the recipient.
757 Parameters concerning known/unknown recipients of relay destinations:
759 relay_domains (Postfix >= 3.0: empty, Postfix < 3.0: $mydestination)
761 What destination domains (and subdomains thereof) this system
762 will relay mail to.
763 relay_recipient_maps (empty)
765 Optional lookup tables with all valid addresses in the domains
766 that match $relay_domains.
767 unknown_relay_recipient_reject_code (550)
769 The numerical Postfix SMTP server reply code when a recipient
770 address matches $relay_domains, and relay_recipient_maps speci‐
771 fies a list of lookup tables that does not match the recipient
772 address.
773 Parameters concerning known/unknown recipients in virtual alias
775 domains:
776 virtual_alias_domains ($virtual_alias_maps)
778 Postfix is final destination for the specified list of virtual
779 alias domains, that is, domains for which all addresses are
780 aliased to addresses in other local or remote domains.
781 virtual_alias_maps ($virtual_maps)
783 Optional lookup tables that alias specific mail addresses or
784 domains to other local or remote address.
785 unknown_virtual_alias_reject_code (550)
787 The Postfix SMTP server reply code when a recipient address
788 matches $virtual_alias_domains, and $virtual_alias_maps speci‐
789 fies a list of lookup tables that does not match the recipient
790 address.
791 Parameters concerning known/unknown recipients in virtual mailbox
793 domains:
794 virtual_mailbox_domains ($virtual_mailbox_maps)
796 Postfix is final destination for the specified list of domains;
797 mail is delivered via the $virtual_transport mail delivery
798 transport.
799 virtual_mailbox_maps (empty)
801 Optional lookup tables with all valid addresses in the domains
802 that match $virtual_mailbox_domains.
803 unknown_virtual_mailbox_reject_code (550)
805 The Postfix SMTP server reply code when a recipient address
806 matches $virtual_mailbox_domains, and $virtual_mailbox_maps
807 specifies a list of lookup tables that does not match the recip‐
808 ient address.
809
811 The following parameters limit resource usage by the SMTP server and/or
812 control client request rates.
813 line_length_limit (2048)
815 Upon input, long lines are chopped up into pieces of at most
816 this length; upon delivery, long lines are reconstructed.
817 queue_minfree (0)
819 The minimal amount of free space in bytes in the queue file sys‐
820 tem that is needed to receive mail.
821 message_size_limit (10240000)
823 The maximal size in bytes of a message, including envelope
824 information.
825 smtpd_recipient_limit (1000)
827 The maximal number of recipients that the Postfix SMTP server
828 accepts per message delivery request.
829 smtpd_timeout (normal: 300s, overload: 10s)
831 The time limit for sending a Postfix SMTP server response and
832 for receiving a remote SMTP client request.
833 smtpd_history_flush_threshold (100)
835 The maximal number of lines in the Postfix SMTP server command
836 history before it is flushed upon receipt of EHLO, RSET, or end
837 of DATA.
838 Available in Postfix version 2.3 and later:
840 smtpd_peername_lookup (yes)
842 Attempt to look up the remote SMTP client hostname, and verify
843 that the name matches the client IP address.
844 The per SMTP client connection count and request rate limits are imple‐
846 mented in co-operation with the anvil(8) service, and are available in
847 Postfix version 2.2 and later.
848 smtpd_client_connection_count_limit (50)
850 How many simultaneous connections any client is allowed to make
851 to this service.
852 smtpd_client_connection_rate_limit (0)
854 The maximal number of connection attempts any client is allowed
855 to make to this service per time unit.
856 smtpd_client_message_rate_limit (0)
858 The maximal number of message delivery requests that any client
859 is allowed to make to this service per time unit, regardless of
860 whether or not Postfix actually accepts those messages.
861 smtpd_client_recipient_rate_limit (0)
863 The maximal number of recipient addresses that any client is
864 allowed to send to this service per time unit, regardless of
865 whether or not Postfix actually accepts those recipients.
866 smtpd_client_event_limit_exceptions ($mynetworks)
868 Clients that are excluded from smtpd_client_*_count/rate_limit
869 restrictions.
870 Available in Postfix version 2.3 and later:
872 smtpd_client_new_tls_session_rate_limit (0)
874 The maximal number of new (i.e., uncached) TLS sessions that a
875 remote SMTP client is allowed to negotiate with this service per
876 time unit.
877 Available in Postfix version 2.9 and later:
879 smtpd_per_record_deadline (normal: no, overload: yes)
881 Change the behavior of the smtpd_timeout and smtpd_start‐
882 tls_timeout time limits, from a time limit per read or write
883 system call, to a time limit to send or receive a complete
884 record (an SMTP command line, SMTP response line, SMTP message
885 content line, or TLS protocol message).
886 Available in Postfix version 3.1 and later:
888 smtpd_client_auth_rate_limit (0)
890 The maximal number of AUTH commands that any client is allowed
891 to send to this service per time unit, regardless of whether or
892 not Postfix actually accepts those commands.
893
895 When a remote SMTP client makes errors, the Postfix SMTP server can
896 insert delays before responding. This can help to slow down run-away
897 software. The behavior is controlled by an error counter that counts
898 the number of errors within an SMTP session that a client makes without
899 delivering mail.
900 smtpd_error_sleep_time (1s)
902 With Postfix version 2.1 and later: the SMTP server response
903 delay after a client has made more than $smtpd_soft_error_limit
904 errors, and fewer than $smtpd_hard_error_limit errors, without
905 delivering mail.
906 smtpd_soft_error_limit (10)
908 The number of errors a remote SMTP client is allowed to make
909 without delivering mail before the Postfix SMTP server slows
910 down all its responses.
911 smtpd_hard_error_limit (normal: 20, overload: 1)
913 The maximal number of errors a remote SMTP client is allowed to
914 make without delivering mail.
915 smtpd_junk_command_limit (normal: 100, overload: 1)
917 The number of junk commands (NOOP, VRFY, ETRN or RSET) that a
918 remote SMTP client can send before the Postfix SMTP server
919 starts to increment the error counter with each junk command.
920 Available in Postfix version 2.1 and later:
922 smtpd_recipient_overshoot_limit (1000)
924 The number of recipients that a remote SMTP client can send in
925 excess of the limit specified with $smtpd_recipient_limit,
926 before the Postfix SMTP server increments the per-session error
927 count for each excess recipient.
928
930 As of version 2.1, Postfix can be configured to delegate access policy
931 decisions to an external server that runs outside Postfix. See the
932 file SMTPD_POLICY_README for more information.
933 smtpd_policy_service_max_idle (300s)
935 The time after which an idle SMTPD policy service connection is
936 closed.
937 smtpd_policy_service_max_ttl (1000s)
939 The time after which an active SMTPD policy service connection
940 is closed.
941 smtpd_policy_service_timeout (100s)
943 The time limit for connecting to, writing to, or receiving from
944 a delegated SMTPD policy server.
945 Available in Postfix version 3.0 and later:
947 smtpd_policy_service_default_action (451 4.3.5 Server configuration
949 problem)
950 The default action when an SMTPD policy service request fails.
951 smtpd_policy_service_request_limit (0)
953 The maximal number of requests per SMTPD policy service connec‐
954 tion, or zero (no limit).
955 smtpd_policy_service_try_limit (2)
957 The maximal number of attempts to send an SMTPD policy service
958 request before giving up.
959 smtpd_policy_service_retry_delay (1s)
961 The delay between attempts to resend a failed SMTPD policy ser‐
962 vice request.
963 Available in Postfix version 3.1 and later:
965 smtpd_policy_service_policy_context (empty)
967 Optional information that the Postfix SMTP server specifies in
968 the "policy_context" attribute of a policy service request
969 (originally, to share the same service endpoint among multiple
970 check_policy_service clients).
971
973 The SMTPD_ACCESS_README document gives an introduction to all the SMTP
974 server access control features.
975 smtpd_delay_reject (yes)
977 Wait until the RCPT TO command before evaluating
978 $smtpd_client_restrictions, $smtpd_helo_restrictions and
979 $smtpd_sender_restrictions, or wait until the ETRN command
980 before evaluating $smtpd_client_restrictions and
981 $smtpd_helo_restrictions.
982 parent_domain_matches_subdomains (see 'postconf -d' output)
984 A list of Postfix features where the pattern "example.com" also
985 matches subdomains of example.com, instead of requiring an
986 explicit ".example.com" pattern.
987 smtpd_client_restrictions (empty)
989 Optional restrictions that the Postfix SMTP server applies in
990 the context of a client connection request.
991 smtpd_helo_required (no)
993 Require that a remote SMTP client introduces itself with the
994 HELO or EHLO command before sending the MAIL command or other
995 commands that require EHLO negotiation.
996 smtpd_helo_restrictions (empty)
998 Optional restrictions that the Postfix SMTP server applies in
999 the context of a client HELO command.
1000 smtpd_sender_restrictions (empty)
1002 Optional restrictions that the Postfix SMTP server applies in
1003 the context of a client MAIL FROM command.
1004 smtpd_recipient_restrictions (see 'postconf -d' output)
1006 Optional restrictions that the Postfix SMTP server applies in
1007 the context of a client RCPT TO command, after
1008 smtpd_relay_restrictions.
1009 smtpd_etrn_restrictions (empty)
1011 Optional restrictions that the Postfix SMTP server applies in
1012 the context of a client ETRN command.
1013 allow_untrusted_routing (no)
1015 Forward mail with sender-specified routing
1016 (user[@%!]remote[@%!]site) from untrusted clients to destina‐
1017 tions matching $relay_domains.
1018 smtpd_restriction_classes (empty)
1020 User-defined aliases for groups of access restrictions.
1021 smtpd_null_access_lookup_key (<>)
1023 The lookup key to be used in SMTP access(5) tables instead of
1024 the null sender address.
1025 permit_mx_backup_networks (empty)
1027 Restrict the use of the permit_mx_backup SMTP access feature to
1028 only domains whose primary MX hosts match the listed networks.
1029 Available in Postfix version 2.0 and later:
1031 smtpd_data_restrictions (empty)
1033 Optional access restrictions that the Postfix SMTP server
1034 applies in the context of the SMTP DATA command.
1035 smtpd_expansion_filter (see 'postconf -d' output)
1037 What characters are allowed in $name expansions of RBL reply
1038 templates.
1039 Available in Postfix version 2.1 and later:
1041 smtpd_reject_unlisted_sender (no)
1043 Request that the Postfix SMTP server rejects mail from unknown
1044 sender addresses, even when no explicit reject_unlisted_sender
1045 access restriction is specified.
1046 smtpd_reject_unlisted_recipient (yes)
1048 Request that the Postfix SMTP server rejects mail for unknown
1049 recipient addresses, even when no explicit
1050 reject_unlisted_recipient access restriction is specified.
1051 Available in Postfix version 2.2 and later:
1053 smtpd_end_of_data_restrictions (empty)
1055 Optional access restrictions that the Postfix SMTP server
1056 applies in the context of the SMTP END-OF-DATA command.
1057 Available in Postfix version 2.10 and later:
1059 smtpd_relay_restrictions (permit_mynetworks, permit_sasl_authenticated,
1061 defer_unauth_destination)
1062 Access restrictions for mail relay control that the Postfix SMTP
1063 server applies in the context of the RCPT TO command, before
1064 smtpd_recipient_restrictions.
1065
1067 Postfix version 2.1 introduces sender and recipient address verifica‐
1068 tion. This feature is implemented by sending probe email messages that
1069 are not actually delivered. This feature is requested via the
1070 reject_unverified_sender and reject_unverified_recipient access
1071 restrictions. The status of verification probes is maintained by the
1072 verify(8) server. See the file ADDRESS_VERIFICATION_README for infor‐
1073 mation about how to configure and operate the Postfix sender/recipient
1074 address verification service.
1075 address_verify_poll_count (normal: 3, overload: 1)
1077 How many times to query the verify(8) service for the completion
1078 of an address verification request in progress.
1079 address_verify_poll_delay (3s)
1081 The delay between queries for the completion of an address veri‐
1082 fication request in progress.
1083 address_verify_sender ($double_bounce_sender)
1085 The sender address to use in address verification probes; prior
1086 to Postfix 2.5 the default was "postmaster".
1087 unverified_sender_reject_code (450)
1089 The numerical Postfix SMTP server response code when a recipient
1090 address is rejected by the reject_unverified_sender restriction.
1091 unverified_recipient_reject_code (450)
1093 The numerical Postfix SMTP server response when a recipient
1094 address is rejected by the reject_unverified_recipient restric‐
1095 tion.
1096 Available in Postfix version 2.6 and later:
1098 unverified_sender_defer_code (450)
1100 The numerical Postfix SMTP server response code when a sender
1101 address probe fails due to a temporary error condition.
1102 unverified_recipient_defer_code (450)
1104 The numerical Postfix SMTP server response when a recipient
1105 address probe fails due to a temporary error condition.
1106 unverified_sender_reject_reason (empty)
1108 The Postfix SMTP server's reply when rejecting mail with
1109 reject_unverified_sender.
1110 unverified_recipient_reject_reason (empty)
1112 The Postfix SMTP server's reply when rejecting mail with
1113 reject_unverified_recipient.
1114 unverified_sender_tempfail_action ($reject_tempfail_action)
1116 The Postfix SMTP server's action when reject_unverified_sender
1117 fails due to a temporary error condition.
1118 unverified_recipient_tempfail_action ($reject_tempfail_action)
1120 The Postfix SMTP server's action when reject_unverified_recipi‐
1121 ent fails due to a temporary error condition.
1122 Available with Postfix 2.9 and later:
1124 address_verify_sender_ttl (0s)
1126 The time between changes in the time-dependent portion of
1127 address verification probe sender addresses.
1128
1130 The following parameters control numerical SMTP reply codes and/or text
1131 responses.
1132 access_map_reject_code (554)
1134 The numerical Postfix SMTP server response code for an access(5)
1135 map "reject" action.
1136 defer_code (450)
1138 The numerical Postfix SMTP server response code when a remote
1139 SMTP client request is rejected by the "defer" restriction.
1140 invalid_hostname_reject_code (501)
1142 The numerical Postfix SMTP server response code when the client
1143 HELO or EHLO command parameter is rejected by the
1144 reject_invalid_helo_hostname restriction.
1145 maps_rbl_reject_code (554)
1147 The numerical Postfix SMTP server response code when a remote
1148 SMTP client request is blocked by the reject_rbl_client,
1149 reject_rhsbl_client, reject_rhsbl_reverse_client,
1150 reject_rhsbl_sender or reject_rhsbl_recipient restriction.
1151 non_fqdn_reject_code (504)
1153 The numerical Postfix SMTP server reply code when a client
1154 request is rejected by the reject_non_fqdn_helo_hostname,
1155 reject_non_fqdn_sender or reject_non_fqdn_recipient restriction.
1156 plaintext_reject_code (450)
1158 The numerical Postfix SMTP server response code when a request
1159 is rejected by the reject_plaintext_session restriction.
1160 reject_code (554)
1162 The numerical Postfix SMTP server response code when a remote
1163 SMTP client request is rejected by the "reject" restriction.
1164 relay_domains_reject_code (554)
1166 The numerical Postfix SMTP server response code when a client
1167 request is rejected by the reject_unauth_destination recipient
1168 restriction.
1169 unknown_address_reject_code (450)
1171 The numerical response code when the Postfix SMTP server rejects
1172 a sender or recipient address because its domain is unknown.
1173 unknown_client_reject_code (450)
1175 The numerical Postfix SMTP server response code when a client
1176 without valid address <=> name mapping is rejected by the
1177 reject_unknown_client_hostname restriction.
1178 unknown_hostname_reject_code (450)
1180 The numerical Postfix SMTP server response code when the host‐
1181 name specified with the HELO or EHLO command is rejected by the
1182 reject_unknown_helo_hostname restriction.
1183 Available in Postfix version 2.0 and later:
1185 default_rbl_reply (see 'postconf -d' output)
1187 The default Postfix SMTP server response template for a request
1188 that is rejected by an RBL-based restriction.
1189 multi_recipient_bounce_reject_code (550)
1191 The numerical Postfix SMTP server response code when a remote
1192 SMTP client request is blocked by the reject_multi_recipi‐
1193 ent_bounce restriction.
1194 rbl_reply_maps (empty)
1196 Optional lookup tables with RBL response templates.
1197 Available in Postfix version 2.6 and later:
1199 access_map_defer_code (450)
1201 The numerical Postfix SMTP server response code for an access(5)
1202 map "defer" action, including "defer_if_permit" or
1203 "defer_if_reject".
1204 reject_tempfail_action (defer_if_permit)
1206 The Postfix SMTP server's action when a reject-type restriction
1207 fails due to a temporary error condition.
1208 unknown_helo_hostname_tempfail_action ($reject_tempfail_action)
1210 The Postfix SMTP server's action when reject_unknown_helo_host‐
1211 name fails due to a temporary error condition.
1212 unknown_address_tempfail_action ($reject_tempfail_action)
1214 The Postfix SMTP server's action when
1215 reject_unknown_sender_domain or reject_unknown_recipient_domain
1216 fail due to a temporary error condition.
1217
1219 config_directory (see 'postconf -d' output)
1220 The default location of the Postfix main.cf and master.cf con‐
1221 figuration files.
1222 daemon_timeout (18000s)
1224 How much time a Postfix daemon process may take to handle a
1225 request before it is terminated by a built-in watchdog timer.
1226 command_directory (see 'postconf -d' output)
1228 The location of all postfix administrative commands.
1229 double_bounce_sender (double-bounce)
1231 The sender address of postmaster notifications that are gener‐
1232 ated by the mail system.
1233 ipc_timeout (3600s)
1235 The time limit for sending or receiving information over an
1236 internal communication channel.
1237 mail_name (Postfix)
1239 The mail system name that is displayed in Received: headers, in
1240 the SMTP greeting banner, and in bounced mail.
1241 mail_owner (postfix)
1243 The UNIX system account that owns the Postfix queue and most
1244 Postfix daemon processes.
1245 max_idle (100s)
1247 The maximum amount of time that an idle Postfix daemon process
1248 waits for an incoming connection before terminating voluntarily.
1249 max_use (100)
1251 The maximal number of incoming connections that a Postfix daemon
1252 process will service before terminating voluntarily.
1253 myhostname (see 'postconf -d' output)
1255 The internet hostname of this mail system.
1256 mynetworks (see 'postconf -d' output)
1258 The list of "trusted" remote SMTP clients that have more privi‐
1259 leges than "strangers".
1260 myorigin ($myhostname)
1262 The domain name that locally-posted mail appears to come from,
1263 and that locally posted mail is delivered to.
1264 process_id (read-only)
1266 The process ID of a Postfix command or daemon process.
1267 process_name (read-only)
1269 The process name of a Postfix command or daemon process.
1270 queue_directory (see 'postconf -d' output)
1272 The location of the Postfix top-level queue directory.
1273 recipient_delimiter (empty)
1275 The set of characters that can separate a user name from its
1276 extension (example: user+foo), or a .forward file name from its
1277 extension (example: .forward+foo).
1278 smtpd_banner ($myhostname ESMTP $mail_name)
1280 The text that follows the 220 status code in the SMTP greeting
1281 banner.
1282 syslog_facility (mail)
1284 The syslog facility of Postfix logging.
1285 syslog_name (see 'postconf -d' output)
1287 A prefix that is prepended to the process name in syslog
1288 records, so that, for example, "smtpd" becomes "prefix/smtpd".
1289 Available in Postfix version 2.2 and later:
1291 smtpd_forbidden_commands (CONNECT, GET, POST)
1293 List of commands that cause the Postfix SMTP server to immedi‐
1294 ately terminate the session with a 221 code.
1295 Available in Postfix version 2.5 and later:
1297 smtpd_client_port_logging (no)
1299 Enable logging of the remote SMTP client port in addition to the
1300 hostname and IP address.
1301 Available in Postfix 3.3 and later:
1303 service_name (read-only)
1305 The master.cf service name of a Postfix daemon process.
1306 Available in Postfix 3.4 and later:
1308 smtpd_reject_footer_maps (empty)
1310 Lookup tables, indexed by the complete Postfix SMTP server 4xx
1311 or 5xx response, with reject footer templates.
1312
1314 anvil(8), connection/rate limiting
1315 cleanup(8), message canonicalization
1316 tlsmgr(8), TLS session and PRNG management
1317 trivial-rewrite(8), address resolver
1318 verify(8), address verification service
1319 postconf(5), configuration parameters
1320 master(5), generic daemon options
1321 master(8), process manager
1322 postlogd(8), Postfix logging
1323 syslogd(8), system logging
1324
1326 Use "postconf readme_directory" or "postconf html_directory" to locate
1327 this information.
1328 ADDRESS_CLASS_README, blocking unknown hosted or relay recipients
1329 ADDRESS_REWRITING_README, Postfix address manipulation
1330 BDAT_README, Postfix CHUNKING support
1331 FILTER_README, external after-queue content filter
1332 LOCAL_RECIPIENT_README, blocking unknown local recipients
1333 MILTER_README, before-queue mail filter applications
1334 SMTPD_ACCESS_README, built-in access policies
1335 SMTPD_POLICY_README, external policy server
1336 SMTPD_PROXY_README, external before-queue content filter
1337 SASL_README, Postfix SASL howto
1338 TLS_README, Postfix STARTTLS howto
1339 VERP_README, Postfix XVERP extension
1340 XCLIENT_README, Postfix XCLIENT extension
1341 XFORWARD_README, Postfix XFORWARD extension
1342
1344 The Secure Mailer license must be distributed with this software.
1345
1347 Wietse Venema
1348 IBM T.J. Watson Research
1349 P.O. Box 704
1350 Yorktown Heights, NY 10598, USA
1351 Wietse Venema
1353 Google, Inc.
1354 111 8th Avenue
1355 New York, NY 10011, USA
1356 SASL support originally by:
1358 Till Franke
1359 SuSE Rhein/Main AG
1360 65760 Eschborn, Germany
1361 TLS support originally by:
1363 Lutz Jaenicke
1364 BTU Cottbus
1365 Allgemeine Elektrotechnik
1366 Universitaetsplatz 3-4
1367 D-03044 Cottbus, Germany
1368 Revised TLS support by:
1370 Victor Duchovni
1371 Morgan Stanley
1372 SMTPD(8)