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) response is
237 unavailable (for example, bad Postfix configuration or Milter
238 failure).
239 milter_macro_daemon_name ($myhostname)
241 The {daemon_name} macro value for Milter (mail filter) applica‐
242 tions.
243 milter_macro_v ($mail_name $mail_version)
245 The {v} macro value for Milter (mail filter) applications.
246 milter_connect_timeout (30s)
248 The time limit for connecting to a Milter (mail filter) applica‐
249 tion, and for negotiating protocol options.
250 milter_command_timeout (30s)
252 The time limit for sending an SMTP command to a Milter (mail
253 filter) application, and for receiving the response.
254 milter_content_timeout (300s)
256 The time limit for sending message content to a Milter (mail
257 filter) application, and for receiving the response.
258 milter_connect_macros (see 'postconf -d' output)
260 The macros that are sent to Milter (mail filter) applications
261 after completion of an SMTP connection.
262 milter_helo_macros (see 'postconf -d' output)
264 The macros that are sent to Milter (mail filter) applications
265 after the SMTP HELO or EHLO command.
266 milter_mail_macros (see 'postconf -d' output)
268 The macros that are sent to Milter (mail filter) applications
269 after the SMTP MAIL FROM command.
270 milter_rcpt_macros (see 'postconf -d' output)
272 The macros that are sent to Milter (mail filter) applications
273 after the SMTP RCPT TO command.
274 milter_data_macros (see 'postconf -d' output)
276 The macros that are sent to version 4 or higher Milter (mail
277 filter) applications after the SMTP DATA command.
278 milter_unknown_command_macros (see 'postconf -d' output)
280 The macros that are sent to version 3 or higher Milter (mail
281 filter) applications after an unknown SMTP command.
282 milter_end_of_header_macros (see 'postconf -d' output)
284 The macros that are sent to Milter (mail filter) applications
285 after the end of the message header.
286 milter_end_of_data_macros (see 'postconf -d' output)
288 The macros that are sent to Milter (mail filter) applications
289 after the message end-of-data.
290 Available in Postfix version 3.1 and later:
292 milter_macro_defaults (empty)
294 Optional list of name=value pairs that specify default values
295 for arbitrary macros that Postfix may send to Milter applica‐
296 tions.
297 Available in Postfix version 3.2 and later:
299 smtpd_milter_maps (empty)
301 Lookup tables with Milter settings per remote SMTP client IP
302 address.
303
305 The following parameters are applicable for both built-in and external
306 content filters.
307 Available in Postfix version 2.1 and later:
309 receive_override_options (empty)
311 Enable or disable recipient validation, built-in content filter‐
312 ing, or address mapping.
313
315 The following parameters are applicable for both before-queue and
316 after-queue content filtering.
317 Available in Postfix version 2.1 and later:
319 smtpd_authorized_xforward_hosts (empty)
321 What remote SMTP clients are allowed to use the XFORWARD fea‐
322 ture.
323
325 Postfix SASL support (RFC 4954) can be used to authenticate remote SMTP
326 clients to the Postfix SMTP server, and to authenticate the Postfix
327 SMTP client to a remote SMTP server. See the SASL_README document for
328 details.
329 broken_sasl_auth_clients (no)
331 Enable interoperability with remote SMTP clients that implement
332 an obsolete version of the AUTH command (RFC 4954).
333 smtpd_sasl_auth_enable (no)
335 Enable SASL authentication in the Postfix SMTP server.
336 smtpd_sasl_local_domain (empty)
338 The name of the Postfix SMTP server's local SASL authentication
339 realm.
340 smtpd_sasl_security_options (noanonymous)
342 Postfix SMTP server SASL security options; as of Postfix 2.3 the
343 list of available features depends on the SASL server implemen‐
344 tation that is selected with smtpd_sasl_type.
345 smtpd_sender_login_maps (empty)
347 Optional lookup table with the SASL login names that own the
348 sender (MAIL FROM) addresses.
349 Available in Postfix version 2.1 and later:
351 smtpd_sasl_exceptions_networks (empty)
353 What remote SMTP clients the Postfix SMTP server will not offer
354 AUTH support to.
355 Available in Postfix version 2.1 and 2.2:
357 smtpd_sasl_application_name (smtpd)
359 The application name that the Postfix SMTP server uses for SASL
360 server initialization.
361 Available in Postfix version 2.3 and later:
363 smtpd_sasl_authenticated_header (no)
365 Report the SASL authenticated user name in the smtpd(8) Received
366 message header.
367 smtpd_sasl_path (smtpd)
369 Implementation-specific information that the Postfix SMTP server
370 passes through to the SASL plug-in implementation that is
371 selected with smtpd_sasl_type.
372 smtpd_sasl_type (cyrus)
374 The SASL plug-in type that the Postfix SMTP server should use
375 for authentication.
376 Available in Postfix version 2.5 and later:
378 cyrus_sasl_config_path (empty)
380 Search path for Cyrus SASL application configuration files, cur‐
381 rently used only to locate the $smtpd_sasl_path.conf file.
382 Available in Postfix version 2.11 and later:
384 smtpd_sasl_service (smtp)
386 The service name that is passed to the SASL plug-in that is
387 selected with smtpd_sasl_type and smtpd_sasl_path.
388 Available in Postfix version 3.4 and later:
390 smtpd_sasl_response_limit (12288)
392 The maximum length of a SASL client's response to a server chal‐
393 lenge.
394
396 Detailed information about STARTTLS configuration may be found in the
397 TLS_README document.
398 smtpd_tls_security_level (empty)
400 The SMTP TLS security level for the Postfix SMTP server; when a
401 non-empty value is specified, this overrides the obsolete param‐
402 eters smtpd_use_tls and smtpd_enforce_tls.
403 smtpd_sasl_tls_security_options ($smtpd_sasl_security_options)
405 The SASL authentication security options that the Postfix SMTP
406 server uses for TLS encrypted SMTP sessions.
407 smtpd_starttls_timeout (see 'postconf -d' output)
409 The time limit for Postfix SMTP server write and read operations
410 during TLS startup and shutdown handshake procedures.
411 smtpd_tls_CAfile (empty)
413 A file containing (PEM format) CA certificates of root CAs
414 trusted to sign either remote SMTP client certificates or inter‐
415 mediate CA certificates.
416 smtpd_tls_CApath (empty)
418 A directory containing (PEM format) CA certificates of root CAs
419 trusted to sign either remote SMTP client certificates or inter‐
420 mediate CA certificates.
421 smtpd_tls_always_issue_session_ids (yes)
423 Force the Postfix SMTP server to issue a TLS session id, even
424 when TLS session caching is turned off (smtpd_tls_ses‐
425 sion_cache_database is empty).
426 smtpd_tls_ask_ccert (no)
428 Ask a remote SMTP client for a client certificate.
429 smtpd_tls_auth_only (no)
431 When TLS encryption is optional in the Postfix SMTP server, do
432 not announce or accept SASL authentication over unencrypted con‐
433 nections.
434 smtpd_tls_ccert_verifydepth (9)
436 The verification depth for remote SMTP client certificates.
437 smtpd_tls_cert_file (empty)
439 File with the Postfix SMTP server RSA certificate in PEM format.
440 smtpd_tls_exclude_ciphers (empty)
442 List of ciphers or cipher types to exclude from the SMTP server
443 cipher list at all TLS security levels.
444 smtpd_tls_dcert_file (empty)
446 File with the Postfix SMTP server DSA certificate in PEM format.
447 smtpd_tls_dh1024_param_file (empty)
449 File with DH parameters that the Postfix SMTP server should use
450 with non-export EDH ciphers.
451 smtpd_tls_dh512_param_file (empty)
453 File with DH parameters that the Postfix SMTP server should use
454 with export-grade EDH ciphers.
455 smtpd_tls_dkey_file ($smtpd_tls_dcert_file)
457 File with the Postfix SMTP server DSA private key in PEM format.
458 smtpd_tls_key_file ($smtpd_tls_cert_file)
460 File with the Postfix SMTP server RSA private key in PEM format.
461 smtpd_tls_loglevel (0)
463 Enable additional Postfix SMTP server logging of TLS activity.
464 smtpd_tls_mandatory_ciphers (medium)
466 The minimum TLS cipher grade that the Postfix SMTP server will
467 use with mandatory TLS encryption.
468 smtpd_tls_mandatory_exclude_ciphers (empty)
470 Additional list of ciphers or cipher types to exclude from the
471 Postfix SMTP server cipher list at mandatory TLS security lev‐
472 els.
473 smtpd_tls_mandatory_protocols (!SSLv2, !SSLv3)
475 The SSL/TLS protocols accepted by the Postfix SMTP server with
476 mandatory TLS encryption.
477 smtpd_tls_received_header (no)
479 Request that the Postfix SMTP server produces Received: message
480 headers that include information about the protocol and cipher
481 used, as well as the remote SMTP client CommonName and client
482 certificate issuer CommonName.
483 smtpd_tls_req_ccert (no)
485 With mandatory TLS encryption, require a trusted remote SMTP
486 client certificate in order to allow TLS connections to proceed.
487 smtpd_tls_wrappermode (no)
489 Run the Postfix SMTP server in the non-standard "wrapper" mode,
490 instead of using the STARTTLS command.
491 tls_daemon_random_bytes (32)
493 The number of pseudo-random bytes that an smtp(8) or smtpd(8)
494 process requests from the tlsmgr(8) server in order to seed its
495 internal pseudo random number generator (PRNG).
496 tls_high_cipherlist (see 'postconf -d' output)
498 The OpenSSL cipherlist for "high" grade ciphers.
499 tls_medium_cipherlist (see 'postconf -d' output)
501 The OpenSSL cipherlist for "medium" or higher grade ciphers.
502 tls_low_cipherlist (see 'postconf -d' output)
504 The OpenSSL cipherlist for "low" or higher grade ciphers.
505 tls_export_cipherlist (see 'postconf -d' output)
507 The OpenSSL cipherlist for "export" or higher grade ciphers.
508 tls_null_cipherlist (eNULL:!aNULL)
510 The OpenSSL cipherlist for "NULL" grade ciphers that provide
511 authentication without encryption.
512 Available in Postfix version 2.5 and later:
514 smtpd_tls_fingerprint_digest (md5)
516 The message digest algorithm to construct remote SMTP
517 client-certificate fingerprints or public key fingerprints
518 (Postfix 2.9 and later) for check_ccert_access and per‐
519 mit_tls_clientcerts.
520 Available in Postfix version 2.6 and later:
522 smtpd_tls_protocols (!SSLv2, !SSLv3)
524 List of TLS protocols that the Postfix SMTP server will exclude
525 or include with opportunistic TLS encryption.
526 smtpd_tls_ciphers (medium)
528 The minimum TLS cipher grade that the Postfix SMTP server will
529 use with opportunistic TLS encryption.
530 smtpd_tls_eccert_file (empty)
532 File with the Postfix SMTP server ECDSA certificate in PEM for‐
533 mat.
534 smtpd_tls_eckey_file ($smtpd_tls_eccert_file)
536 File with the Postfix SMTP server ECDSA private key in PEM for‐
537 mat.
538 smtpd_tls_eecdh_grade (see 'postconf -d' output)
540 The Postfix SMTP server security grade for ephemeral ellip‐
541 tic-curve Diffie-Hellman (EECDH) key exchange.
542 tls_eecdh_strong_curve (prime256v1)
544 The elliptic curve used by the Postfix SMTP server for sensibly
545 strong ephemeral ECDH key exchange.
546 tls_eecdh_ultra_curve (secp384r1)
548 The elliptic curve used by the Postfix SMTP server for maximally
549 strong ephemeral ECDH key exchange.
550 Available in Postfix version 2.8 and later:
552 tls_preempt_cipherlist (no)
554 With SSLv3 and later, use the Postfix SMTP server's cipher pref‐
555 erence order instead of the remote client's cipher preference
556 order.
557 tls_disable_workarounds (see 'postconf -d' output)
559 List or bit-mask of OpenSSL bug work-arounds to disable.
560 Available in Postfix version 2.11 and later:
562 tlsmgr_service_name (tlsmgr)
564 The name of the tlsmgr(8) service entry in master.cf.
565 Available in Postfix version 3.0 and later:
567 tls_session_ticket_cipher (Postfix >= 3.0: aes-256-cbc, Postfix < 3.0:
569 aes-128-cbc)
570 Algorithm used to encrypt RFC5077 TLS session tickets.
571 Available in Postfix version 3.2 and later:
573 tls_eecdh_auto_curves (see 'postconf -d' output)
575 The prioritized list of elliptic curves supported by the Postfix
576 SMTP client and server.
577 Available in Postfix version 3.4 and later:
579 smtpd_tls_chain_files (empty)
581 List of one or more PEM files, each holding one or more private
582 keys directly followed by a corresponding certificate chain.
583 tls_server_sni_maps (empty)
585 Optional lookup tables that map names received from remote SMTP
586 clients via the TLS Server Name Indication (SNI) extension to
587 the appropriate keys and certificate chains.
588 Available in Postfix 3.5, 3.4.6, 3.3.5, 3.2.10, 3.1.13 and later:
590 tls_fast_shutdown_enable (yes)
592 A workaround for implementations that hang Postfix while shut‐
593 ting down a TLS session, until Postfix times out.
594 Available in Postfix 3.5 and later:
596 info_log_address_format (external)
598 The email address form that will be used in non-debug logging
599 (info, warning, etc.).
600
602 The following configuration parameters exist for compatibility with
603 Postfix versions before 2.3. Support for these will be removed in a
604 future release.
605 smtpd_use_tls (no)
607 Opportunistic TLS: announce STARTTLS support to remote SMTP
608 clients, but do not require that clients use TLS encryption.
609 smtpd_enforce_tls (no)
611 Mandatory TLS: announce STARTTLS support to remote SMTP clients,
612 and require that clients use TLS encryption.
613 smtpd_tls_cipherlist (empty)
615 Obsolete Postfix < 2.3 control for the Postfix SMTP server TLS
616 cipher list.
617
619 Preliminary SMTPUTF8 support is introduced with Postfix 3.0.
620 smtputf8_enable (yes)
622 Enable preliminary SMTPUTF8 support for the protocols described
623 in RFC 6531..6533.
624 strict_smtputf8 (no)
626 Enable stricter enforcement of the SMTPUTF8 protocol.
627 smtputf8_autodetect_classes (sendmail, verify)
629 Detect that a message requires SMTPUTF8 support for the speci‐
630 fied mail origin classes.
631 Available in Postfix version 3.2 and later:
633 enable_idna2003_compatibility (no)
635 Enable 'transitional' compatibility between IDNA2003 and
636 IDNA2008, when converting UTF-8 domain names to/from the ASCII
637 form that is used for DNS lookups.
638
640 With VERP style delivery, each recipient of a message receives a cus‐
641 tomized copy of the message with his/her own recipient address encoded
642 in the envelope sender address. The VERP_README file describes config‐
643 uration and operation details of Postfix support for variable envelope
644 return path addresses. VERP style delivery is requested with the SMTP
645 XVERP command or with the "sendmail -V" command-line option and is
646 available in Postfix version 1.1 and later.
647 default_verp_delimiters (+=)
649 The two default VERP delimiter characters.
650 verp_delimiter_filter (-=+)
652 The characters Postfix accepts as VERP delimiter characters on
653 the Postfix sendmail(1) command line and in SMTP commands.
654 Available in Postfix version 1.1 and 2.0:
656 authorized_verp_clients ($mynetworks)
658 What remote SMTP clients are allowed to specify the XVERP com‐
659 mand.
660 Available in Postfix version 2.1 and later:
662 smtpd_authorized_verp_clients ($authorized_verp_clients)
664 What remote SMTP clients are allowed to specify the XVERP com‐
665 mand.
666
668 The DEBUG_README document describes how to debug parts of the Postfix
669 mail system. The methods vary from making the software log a lot of
670 detail, to running some daemon processes under control of a call tracer
671 or debugger.
672 debug_peer_level (2)
674 The increment in verbose logging level when a remote client or
675 server matches a pattern in the debug_peer_list parameter.
676 debug_peer_list (empty)
678 Optional list of remote client or server hostname or network
679 address patterns that cause the verbose logging level to
680 increase by the amount specified in $debug_peer_level.
681 error_notice_recipient (postmaster)
683 The recipient of postmaster notifications about mail delivery
684 problems that are caused by policy, resource, software or proto‐
685 col errors.
686 internal_mail_filter_classes (empty)
688 What categories of Postfix-generated mail are subject to
689 before-queue content inspection by non_smtpd_milters,
690 header_checks and body_checks.
691 notify_classes (resource, software)
693 The list of error classes that are reported to the postmaster.
694 smtpd_reject_footer (empty)
696 Optional information that is appended after each Postfix SMTP
697 server 4XX or 5XX response.
698 soft_bounce (no)
700 Safety net to keep mail queued that would otherwise be returned
701 to the sender.
702 Available in Postfix version 2.1 and later:
704 smtpd_authorized_xclient_hosts (empty)
706 What remote SMTP clients are allowed to use the XCLIENT feature.
707 Available in Postfix version 2.10 and later:
709 smtpd_log_access_permit_actions (empty)
711 Enable logging of the named "permit" actions in SMTP server
712 access lists (by default, the SMTP server logs "reject" actions
713 but not "permit" actions).
714
716 As of Postfix version 2.0, the SMTP server rejects mail for unknown
717 recipients. This prevents the mail queue from clogging up with undeliv‐
718 erable MAILER-DAEMON messages. Additional information on this topic is
719 in the LOCAL_RECIPIENT_README and ADDRESS_CLASS_README documents.
720 show_user_unknown_table_name (yes)
722 Display the name of the recipient table in the "User unknown"
723 responses.
724 canonical_maps (empty)
726 Optional address mapping lookup tables for message headers and
727 envelopes.
728 recipient_canonical_maps (empty)
730 Optional address mapping lookup tables for envelope and header
731 recipient addresses.
732 sender_canonical_maps (empty)
734 Optional address mapping lookup tables for envelope and header
735 sender addresses.
736 Parameters concerning known/unknown local recipients:
738 mydestination ($myhostname, localhost.$mydomain, localhost)
740 The list of domains that are delivered via the $local_transport
741 mail delivery transport.
742 inet_interfaces (all)
744 The network interface addresses that this mail system receives
745 mail on.
746 proxy_interfaces (empty)
748 The network interface addresses that this mail system receives
749 mail on by way of a proxy or network address translation unit.
750 inet_protocols (all)
752 The Internet protocols Postfix will attempt to use when making
753 or accepting connections.
754 local_recipient_maps (proxy:unix:passwd.byname $alias_maps)
756 Lookup tables with all names or addresses of local recipients: a
757 recipient address is local when its domain matches $mydestina‐
758 tion, $inet_interfaces or $proxy_interfaces.
759 unknown_local_recipient_reject_code (550)
761 The numerical Postfix SMTP server response code when a recipient
762 address is local, and $local_recipient_maps specifies a list of
763 lookup tables that does not match the recipient.
764 Parameters concerning known/unknown recipients of relay destinations:
766 relay_domains (Postfix >= 3.0: empty, Postfix < 3.0: $mydestination)
768 What destination domains (and subdomains thereof) this system
769 will relay mail to.
770 relay_recipient_maps (empty)
772 Optional lookup tables with all valid addresses in the domains
773 that match $relay_domains.
774 unknown_relay_recipient_reject_code (550)
776 The numerical Postfix SMTP server reply code when a recipient
777 address matches $relay_domains, and relay_recipient_maps speci‐
778 fies a list of lookup tables that does not match the recipient
779 address.
780 Parameters concerning known/unknown recipients in virtual alias
782 domains:
783 virtual_alias_domains ($virtual_alias_maps)
785 Postfix is final destination for the specified list of virtual
786 alias domains, that is, domains for which all addresses are
787 aliased to addresses in other local or remote domains.
788 virtual_alias_maps ($virtual_maps)
790 Optional lookup tables that alias specific mail addresses or
791 domains to other local or remote address.
792 unknown_virtual_alias_reject_code (550)
794 The Postfix SMTP server reply code when a recipient address
795 matches $virtual_alias_domains, and $virtual_alias_maps speci‐
796 fies a list of lookup tables that does not match the recipient
797 address.
798 Parameters concerning known/unknown recipients in virtual mailbox
800 domains:
801 virtual_mailbox_domains ($virtual_mailbox_maps)
803 Postfix is final destination for the specified list of domains;
804 mail is delivered via the $virtual_transport mail delivery
805 transport.
806 virtual_mailbox_maps (empty)
808 Optional lookup tables with all valid addresses in the domains
809 that match $virtual_mailbox_domains.
810 unknown_virtual_mailbox_reject_code (550)
812 The Postfix SMTP server reply code when a recipient address
813 matches $virtual_mailbox_domains, and $virtual_mailbox_maps
814 specifies a list of lookup tables that does not match the recip‐
815 ient address.
816
818 The following parameters limit resource usage by the SMTP server and/or
819 control client request rates.
820 line_length_limit (2048)
822 Upon input, long lines are chopped up into pieces of at most
823 this length; upon delivery, long lines are reconstructed.
824 queue_minfree (0)
826 The minimal amount of free space in bytes in the queue file sys‐
827 tem that is needed to receive mail.
828 message_size_limit (10240000)
830 The maximal size in bytes of a message, including envelope
831 information.
832 smtpd_recipient_limit (1000)
834 The maximal number of recipients that the Postfix SMTP server
835 accepts per message delivery request.
836 smtpd_timeout (normal: 300s, overload: 10s)
838 The time limit for sending a Postfix SMTP server response and
839 for receiving a remote SMTP client request.
840 smtpd_history_flush_threshold (100)
842 The maximal number of lines in the Postfix SMTP server command
843 history before it is flushed upon receipt of EHLO, RSET, or end
844 of DATA.
845 Available in Postfix version 2.3 and later:
847 smtpd_peername_lookup (yes)
849 Attempt to look up the remote SMTP client hostname, and verify
850 that the name matches the client IP address.
851 The per SMTP client connection count and request rate limits are imple‐
853 mented in co-operation with the anvil(8) service, and are available in
854 Postfix version 2.2 and later.
855 smtpd_client_connection_count_limit (50)
857 How many simultaneous connections any client is allowed to make
858 to this service.
859 smtpd_client_connection_rate_limit (0)
861 The maximal number of connection attempts any client is allowed
862 to make to this service per time unit.
863 smtpd_client_message_rate_limit (0)
865 The maximal number of message delivery requests that any client
866 is allowed to make to this service per time unit, regardless of
867 whether or not Postfix actually accepts those messages.
868 smtpd_client_recipient_rate_limit (0)
870 The maximal number of recipient addresses that any client is
871 allowed to send to this service per time unit, regardless of
872 whether or not Postfix actually accepts those recipients.
873 smtpd_client_event_limit_exceptions ($mynetworks)
875 Clients that are excluded from smtpd_client_*_count/rate_limit
876 restrictions.
877 Available in Postfix version 2.3 and later:
879 smtpd_client_new_tls_session_rate_limit (0)
881 The maximal number of new (i.e., uncached) TLS sessions that a
882 remote SMTP client is allowed to negotiate with this service per
883 time unit.
884 Available in Postfix version 2.9 and later:
886 smtpd_per_record_deadline (normal: no, overload: yes)
888 Change the behavior of the smtpd_timeout and smtpd_start‐
889 tls_timeout time limits, from a time limit per read or write
890 system call, to a time limit to send or receive a complete
891 record (an SMTP command line, SMTP response line, SMTP message
892 content line, or TLS protocol message).
893 Available in Postfix version 3.1 and later:
895 smtpd_client_auth_rate_limit (0)
897 The maximal number of AUTH commands that any client is allowed
898 to send to this service per time unit, regardless of whether or
899 not Postfix actually accepts those commands.
900
902 When a remote SMTP client makes errors, the Postfix SMTP server can
903 insert delays before responding. This can help to slow down run-away
904 software. The behavior is controlled by an error counter that counts
905 the number of errors within an SMTP session that a client makes without
906 delivering mail.
907 smtpd_error_sleep_time (1s)
909 With Postfix version 2.1 and later: the SMTP server response
910 delay after a client has made more than $smtpd_soft_error_limit
911 errors, and fewer than $smtpd_hard_error_limit errors, without
912 delivering mail.
913 smtpd_soft_error_limit (10)
915 The number of errors a remote SMTP client is allowed to make
916 without delivering mail before the Postfix SMTP server slows
917 down all its responses.
918 smtpd_hard_error_limit (normal: 20, overload: 1)
920 The maximal number of errors a remote SMTP client is allowed to
921 make without delivering mail.
922 smtpd_junk_command_limit (normal: 100, overload: 1)
924 The number of junk commands (NOOP, VRFY, ETRN or RSET) that a
925 remote SMTP client can send before the Postfix SMTP server
926 starts to increment the error counter with each junk command.
927 Available in Postfix version 2.1 and later:
929 smtpd_recipient_overshoot_limit (1000)
931 The number of recipients that a remote SMTP client can send in
932 excess of the limit specified with $smtpd_recipient_limit,
933 before the Postfix SMTP server increments the per-session error
934 count for each excess recipient.
935
937 As of version 2.1, Postfix can be configured to delegate access policy
938 decisions to an external server that runs outside Postfix. See the
939 file SMTPD_POLICY_README for more information.
940 smtpd_policy_service_max_idle (300s)
942 The time after which an idle SMTPD policy service connection is
943 closed.
944 smtpd_policy_service_max_ttl (1000s)
946 The time after which an active SMTPD policy service connection
947 is closed.
948 smtpd_policy_service_timeout (100s)
950 The time limit for connecting to, writing to, or receiving from
951 a delegated SMTPD policy server.
952 Available in Postfix version 3.0 and later:
954 smtpd_policy_service_default_action (451 4.3.5 Server configuration
956 problem)
957 The default action when an SMTPD policy service request fails.
958 smtpd_policy_service_request_limit (0)
960 The maximal number of requests per SMTPD policy service connec‐
961 tion, or zero (no limit).
962 smtpd_policy_service_try_limit (2)
964 The maximal number of attempts to send an SMTPD policy service
965 request before giving up.
966 smtpd_policy_service_retry_delay (1s)
968 The delay between attempts to resend a failed SMTPD policy ser‐
969 vice request.
970 Available in Postfix version 3.1 and later:
972 smtpd_policy_service_policy_context (empty)
974 Optional information that the Postfix SMTP server specifies in
975 the "policy_context" attribute of a policy service request
976 (originally, to share the same service endpoint among multiple
977 check_policy_service clients).
978
980 The SMTPD_ACCESS_README document gives an introduction to all the SMTP
981 server access control features.
982 smtpd_delay_reject (yes)
984 Wait until the RCPT TO command before evaluating
985 $smtpd_client_restrictions, $smtpd_helo_restrictions and
986 $smtpd_sender_restrictions, or wait until the ETRN command
987 before evaluating $smtpd_client_restrictions and
988 $smtpd_helo_restrictions.
989 parent_domain_matches_subdomains (see 'postconf -d' output)
991 A list of Postfix features where the pattern "example.com" also
992 matches subdomains of example.com, instead of requiring an
993 explicit ".example.com" pattern.
994 smtpd_client_restrictions (empty)
996 Optional restrictions that the Postfix SMTP server applies in
997 the context of a client connection request.
998 smtpd_helo_required (no)
1000 Require that a remote SMTP client introduces itself with the
1001 HELO or EHLO command before sending the MAIL command or other
1002 commands that require EHLO negotiation.
1003 smtpd_helo_restrictions (empty)
1005 Optional restrictions that the Postfix SMTP server applies in
1006 the context of a client HELO command.
1007 smtpd_sender_restrictions (empty)
1009 Optional restrictions that the Postfix SMTP server applies in
1010 the context of a client MAIL FROM command.
1011 smtpd_recipient_restrictions (see 'postconf -d' output)
1013 Optional restrictions that the Postfix SMTP server applies in
1014 the context of a client RCPT TO command, after
1015 smtpd_relay_restrictions.
1016 smtpd_etrn_restrictions (empty)
1018 Optional restrictions that the Postfix SMTP server applies in
1019 the context of a client ETRN command.
1020 allow_untrusted_routing (no)
1022 Forward mail with sender-specified routing
1023 (user[@%!]remote[@%!]site) from untrusted clients to destina‐
1024 tions matching $relay_domains.
1025 smtpd_restriction_classes (empty)
1027 User-defined aliases for groups of access restrictions.
1028 smtpd_null_access_lookup_key (<>)
1030 The lookup key to be used in SMTP access(5) tables instead of
1031 the null sender address.
1032 permit_mx_backup_networks (empty)
1034 Restrict the use of the permit_mx_backup SMTP access feature to
1035 only domains whose primary MX hosts match the listed networks.
1036 Available in Postfix version 2.0 and later:
1038 smtpd_data_restrictions (empty)
1040 Optional access restrictions that the Postfix SMTP server
1041 applies in the context of the SMTP DATA command.
1042 smtpd_expansion_filter (see 'postconf -d' output)
1044 What characters are allowed in $name expansions of RBL reply
1045 templates.
1046 Available in Postfix version 2.1 and later:
1048 smtpd_reject_unlisted_sender (no)
1050 Request that the Postfix SMTP server rejects mail from unknown
1051 sender addresses, even when no explicit reject_unlisted_sender
1052 access restriction is specified.
1053 smtpd_reject_unlisted_recipient (yes)
1055 Request that the Postfix SMTP server rejects mail for unknown
1056 recipient addresses, even when no explicit
1057 reject_unlisted_recipient access restriction is specified.
1058 Available in Postfix version 2.2 and later:
1060 smtpd_end_of_data_restrictions (empty)
1062 Optional access restrictions that the Postfix SMTP server
1063 applies in the context of the SMTP END-OF-DATA command.
1064 Available in Postfix version 2.10 and later:
1066 smtpd_relay_restrictions (permit_mynetworks, permit_sasl_authenticated,
1068 defer_unauth_destination)
1069 Access restrictions for mail relay control that the Postfix SMTP
1070 server applies in the context of the RCPT TO command, before
1071 smtpd_recipient_restrictions.
1072
1074 Postfix version 2.1 introduces sender and recipient address verifica‐
1075 tion. This feature is implemented by sending probe email messages that
1076 are not actually delivered. This feature is requested via the
1077 reject_unverified_sender and reject_unverified_recipient access
1078 restrictions. The status of verification probes is maintained by the
1079 verify(8) server. See the file ADDRESS_VERIFICATION_README for infor‐
1080 mation about how to configure and operate the Postfix sender/recipient
1081 address verification service.
1082 address_verify_poll_count (normal: 3, overload: 1)
1084 How many times to query the verify(8) service for the completion
1085 of an address verification request in progress.
1086 address_verify_poll_delay (3s)
1088 The delay between queries for the completion of an address veri‐
1089 fication request in progress.
1090 address_verify_sender ($double_bounce_sender)
1092 The sender address to use in address verification probes; prior
1093 to Postfix 2.5 the default was "postmaster".
1094 unverified_sender_reject_code (450)
1096 The numerical Postfix SMTP server response code when a recipient
1097 address is rejected by the reject_unverified_sender restriction.
1098 unverified_recipient_reject_code (450)
1100 The numerical Postfix SMTP server response when a recipient
1101 address is rejected by the reject_unverified_recipient restric‐
1102 tion.
1103 Available in Postfix version 2.6 and later:
1105 unverified_sender_defer_code (450)
1107 The numerical Postfix SMTP server response code when a sender
1108 address probe fails due to a temporary error condition.
1109 unverified_recipient_defer_code (450)
1111 The numerical Postfix SMTP server response when a recipient
1112 address probe fails due to a temporary error condition.
1113 unverified_sender_reject_reason (empty)
1115 The Postfix SMTP server's reply when rejecting mail with
1116 reject_unverified_sender.
1117 unverified_recipient_reject_reason (empty)
1119 The Postfix SMTP server's reply when rejecting mail with
1120 reject_unverified_recipient.
1121 unverified_sender_tempfail_action ($reject_tempfail_action)
1123 The Postfix SMTP server's action when reject_unverified_sender
1124 fails due to a temporary error condition.
1125 unverified_recipient_tempfail_action ($reject_tempfail_action)
1127 The Postfix SMTP server's action when reject_unverified_recipi‐
1128 ent fails due to a temporary error condition.
1129 Available with Postfix 2.9 and later:
1131 address_verify_sender_ttl (0s)
1133 The time between changes in the time-dependent portion of
1134 address verification probe sender addresses.
1135
1137 The following parameters control numerical SMTP reply codes and/or text
1138 responses.
1139 access_map_reject_code (554)
1141 The numerical Postfix SMTP server response code for an access(5)
1142 map "reject" action.
1143 defer_code (450)
1145 The numerical Postfix SMTP server response code when a remote
1146 SMTP client request is rejected by the "defer" restriction.
1147 invalid_hostname_reject_code (501)
1149 The numerical Postfix SMTP server response code when the client
1150 HELO or EHLO command parameter is rejected by the
1151 reject_invalid_helo_hostname restriction.
1152 maps_rbl_reject_code (554)
1154 The numerical Postfix SMTP server response code when a remote
1155 SMTP client request is blocked by the reject_rbl_client,
1156 reject_rhsbl_client, reject_rhsbl_reverse_client,
1157 reject_rhsbl_sender or reject_rhsbl_recipient restriction.
1158 non_fqdn_reject_code (504)
1160 The numerical Postfix SMTP server reply code when a client
1161 request is rejected by the reject_non_fqdn_helo_hostname,
1162 reject_non_fqdn_sender or reject_non_fqdn_recipient restriction.
1163 plaintext_reject_code (450)
1165 The numerical Postfix SMTP server response code when a request
1166 is rejected by the reject_plaintext_session restriction.
1167 reject_code (554)
1169 The numerical Postfix SMTP server response code when a remote
1170 SMTP client request is rejected by the "reject" restriction.
1171 relay_domains_reject_code (554)
1173 The numerical Postfix SMTP server response code when a client
1174 request is rejected by the reject_unauth_destination recipient
1175 restriction.
1176 unknown_address_reject_code (450)
1178 The numerical response code when the Postfix SMTP server rejects
1179 a sender or recipient address because its domain is unknown.
1180 unknown_client_reject_code (450)
1182 The numerical Postfix SMTP server response code when a client
1183 without valid address <=> name mapping is rejected by the
1184 reject_unknown_client_hostname restriction.
1185 unknown_hostname_reject_code (450)
1187 The numerical Postfix SMTP server response code when the host‐
1188 name specified with the HELO or EHLO command is rejected by the
1189 reject_unknown_helo_hostname restriction.
1190 Available in Postfix version 2.0 and later:
1192 default_rbl_reply (see 'postconf -d' output)
1194 The default Postfix SMTP server response template for a request
1195 that is rejected by an RBL-based restriction.
1196 multi_recipient_bounce_reject_code (550)
1198 The numerical Postfix SMTP server response code when a remote
1199 SMTP client request is blocked by the reject_multi_recipi‐
1200 ent_bounce restriction.
1201 rbl_reply_maps (empty)
1203 Optional lookup tables with RBL response templates.
1204 Available in Postfix version 2.6 and later:
1206 access_map_defer_code (450)
1208 The numerical Postfix SMTP server response code for an access(5)
1209 map "defer" action, including "defer_if_permit" or
1210 "defer_if_reject".
1211 reject_tempfail_action (defer_if_permit)
1213 The Postfix SMTP server's action when a reject-type restriction
1214 fails due to a temporary error condition.
1215 unknown_helo_hostname_tempfail_action ($reject_tempfail_action)
1217 The Postfix SMTP server's action when reject_unknown_helo_host‐
1218 name fails due to a temporary error condition.
1219 unknown_address_tempfail_action ($reject_tempfail_action)
1221 The Postfix SMTP server's action when
1222 reject_unknown_sender_domain or reject_unknown_recipient_domain
1223 fail due to a temporary error condition.
1224
1226 config_directory (see 'postconf -d' output)
1227 The default location of the Postfix main.cf and master.cf con‐
1228 figuration files.
1229 daemon_timeout (18000s)
1231 How much time a Postfix daemon process may take to handle a
1232 request before it is terminated by a built-in watchdog timer.
1233 command_directory (see 'postconf -d' output)
1235 The location of all postfix administrative commands.
1236 double_bounce_sender (double-bounce)
1238 The sender address of postmaster notifications that are gener‐
1239 ated by the mail system.
1240 ipc_timeout (3600s)
1242 The time limit for sending or receiving information over an
1243 internal communication channel.
1244 mail_name (Postfix)
1246 The mail system name that is displayed in Received: headers, in
1247 the SMTP greeting banner, and in bounced mail.
1248 mail_owner (postfix)
1250 The UNIX system account that owns the Postfix queue and most
1251 Postfix daemon processes.
1252 max_idle (100s)
1254 The maximum amount of time that an idle Postfix daemon process
1255 waits for an incoming connection before terminating voluntarily.
1256 max_use (100)
1258 The maximal number of incoming connections that a Postfix daemon
1259 process will service before terminating voluntarily.
1260 myhostname (see 'postconf -d' output)
1262 The internet hostname of this mail system.
1263 mynetworks (see 'postconf -d' output)
1265 The list of "trusted" remote SMTP clients that have more privi‐
1266 leges than "strangers".
1267 myorigin ($myhostname)
1269 The domain name that locally-posted mail appears to come from,
1270 and that locally posted mail is delivered to.
1271 process_id (read-only)
1273 The process ID of a Postfix command or daemon process.
1274 process_name (read-only)
1276 The process name of a Postfix command or daemon process.
1277 queue_directory (see 'postconf -d' output)
1279 The location of the Postfix top-level queue directory.
1280 recipient_delimiter (empty)
1282 The set of characters that can separate a user name from its
1283 extension (example: user+foo), or a .forward file name from its
1284 extension (example: .forward+foo).
1285 smtpd_banner ($myhostname ESMTP $mail_name)
1287 The text that follows the 220 status code in the SMTP greeting
1288 banner.
1289 syslog_facility (mail)
1291 The syslog facility of Postfix logging.
1292 syslog_name (see 'postconf -d' output)
1294 A prefix that is prepended to the process name in syslog
1295 records, so that, for example, "smtpd" becomes "prefix/smtpd".
1296 Available in Postfix version 2.2 and later:
1298 smtpd_forbidden_commands (CONNECT, GET, POST)
1300 List of commands that cause the Postfix SMTP server to immedi‐
1301 ately terminate the session with a 221 code.
1302 Available in Postfix version 2.5 and later:
1304 smtpd_client_port_logging (no)
1306 Enable logging of the remote SMTP client port in addition to the
1307 hostname and IP address.
1308 Available in Postfix 3.3 and later:
1310 service_name (read-only)
1312 The master.cf service name of a Postfix daemon process.
1313 Available in Postfix 3.4 and later:
1315 smtpd_reject_footer_maps (empty)
1317 Lookup tables, indexed by the complete Postfix SMTP server 4xx
1318 or 5xx response, with reject footer templates.
1319
1321 anvil(8), connection/rate limiting
1322 cleanup(8), message canonicalization
1323 tlsmgr(8), TLS session and PRNG management
1324 trivial-rewrite(8), address resolver
1325 verify(8), address verification service
1326 postconf(5), configuration parameters
1327 master(5), generic daemon options
1328 master(8), process manager
1329 postlogd(8), Postfix logging
1330 syslogd(8), system logging
1331
1333 Use "postconf readme_directory" or "postconf html_directory" to locate
1334 this information.
1335 ADDRESS_CLASS_README, blocking unknown hosted or relay recipients
1336 ADDRESS_REWRITING_README, Postfix address manipulation
1337 BDAT_README, Postfix CHUNKING support
1338 FILTER_README, external after-queue content filter
1339 LOCAL_RECIPIENT_README, blocking unknown local recipients
1340 MILTER_README, before-queue mail filter applications
1341 SMTPD_ACCESS_README, built-in access policies
1342 SMTPD_POLICY_README, external policy server
1343 SMTPD_PROXY_README, external before-queue content filter
1344 SASL_README, Postfix SASL howto
1345 TLS_README, Postfix STARTTLS howto
1346 VERP_README, Postfix XVERP extension
1347 XCLIENT_README, Postfix XCLIENT extension
1348 XFORWARD_README, Postfix XFORWARD extension
1349
1351 The Secure Mailer license must be distributed with this software.
1352
1354 Wietse Venema
1355 IBM T.J. Watson Research
1356 P.O. Box 704
1357 Yorktown Heights, NY 10598, USA
1358 Wietse Venema
1360 Google, Inc.
1361 111 8th Avenue
1362 New York, NY 10011, USA
1363 SASL support originally by:
1365 Till Franke
1366 SuSE Rhein/Main AG
1367 65760 Eschborn, Germany
1368 TLS support originally by:
1370 Lutz Jaenicke
1371 BTU Cottbus
1372 Allgemeine Elektrotechnik
1373 Universitaetsplatz 3-4
1374 D-03044 Cottbus, Germany
1375 Revised TLS support by:
1377 Victor Duchovni
1378 Morgan Stanley
1379 SMTPD(8)