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
589 The following configuration parameters exist for compatibility with
590 Postfix versions before 2.3. Support for these will be removed in a
591 future release.
592 smtpd_use_tls (no)
594 Opportunistic TLS: announce STARTTLS support to remote SMTP
595 clients, but do not require that clients use TLS encryption.
596 smtpd_enforce_tls (no)
598 Mandatory TLS: announce STARTTLS support to remote SMTP clients,
599 and require that clients use TLS encryption.
600 smtpd_tls_cipherlist (empty)
602 Obsolete Postfix < 2.3 control for the Postfix SMTP server TLS
603 cipher list.
604
606 Preliminary SMTPUTF8 support is introduced with Postfix 3.0.
607 smtputf8_enable (yes)
609 Enable preliminary SMTPUTF8 support for the protocols described
610 in RFC 6531..6533.
611 strict_smtputf8 (no)
613 Enable stricter enforcement of the SMTPUTF8 protocol.
614 smtputf8_autodetect_classes (sendmail, verify)
616 Detect that a message requires SMTPUTF8 support for the speci‐
617 fied mail origin classes.
618 Available in Postfix version 3.2 and later:
620 enable_idna2003_compatibility (no)
622 Enable 'transitional' compatibility between IDNA2003 and
623 IDNA2008, when converting UTF-8 domain names to/from the ASCII
624 form that is used for DNS lookups.
625
627 With VERP style delivery, each recipient of a message receives a cus‐
628 tomized copy of the message with his/her own recipient address encoded
629 in the envelope sender address. The VERP_README file describes config‐
630 uration and operation details of Postfix support for variable envelope
631 return path addresses. VERP style delivery is requested with the SMTP
632 XVERP command or with the "sendmail -V" command-line option and is
633 available in Postfix version 1.1 and later.
634 default_verp_delimiters (+=)
636 The two default VERP delimiter characters.
637 verp_delimiter_filter (-=+)
639 The characters Postfix accepts as VERP delimiter characters on
640 the Postfix sendmail(1) command line and in SMTP commands.
641 Available in Postfix version 1.1 and 2.0:
643 authorized_verp_clients ($mynetworks)
645 What remote SMTP clients are allowed to specify the XVERP com‐
646 mand.
647 Available in Postfix version 2.1 and later:
649 smtpd_authorized_verp_clients ($authorized_verp_clients)
651 What remote SMTP clients are allowed to specify the XVERP com‐
652 mand.
653
655 The DEBUG_README document describes how to debug parts of the Postfix
656 mail system. The methods vary from making the software log a lot of
657 detail, to running some daemon processes under control of a call tracer
658 or debugger.
659 debug_peer_level (2)
661 The increment in verbose logging level when a remote client or
662 server matches a pattern in the debug_peer_list parameter.
663 debug_peer_list (empty)
665 Optional list of remote client or server hostname or network
666 address patterns that cause the verbose logging level to
667 increase by the amount specified in $debug_peer_level.
668 error_notice_recipient (postmaster)
670 The recipient of postmaster notifications about mail delivery
671 problems that are caused by policy, resource, software or proto‐
672 col errors.
673 internal_mail_filter_classes (empty)
675 What categories of Postfix-generated mail are subject to
676 before-queue content inspection by non_smtpd_milters,
677 header_checks and body_checks.
678 notify_classes (resource, software)
680 The list of error classes that are reported to the postmaster.
681 smtpd_reject_footer (empty)
683 Optional information that is appended after each Postfix SMTP
684 server 4XX or 5XX response.
685 soft_bounce (no)
687 Safety net to keep mail queued that would otherwise be returned
688 to the sender.
689 Available in Postfix version 2.1 and later:
691 smtpd_authorized_xclient_hosts (empty)
693 What remote SMTP clients are allowed to use the XCLIENT feature.
694 Available in Postfix version 2.10 and later:
696 smtpd_log_access_permit_actions (empty)
698 Enable logging of the named "permit" actions in SMTP server
699 access lists (by default, the SMTP server logs "reject" actions
700 but not "permit" actions).
701
703 As of Postfix version 2.0, the SMTP server rejects mail for unknown
704 recipients. This prevents the mail queue from clogging up with undeliv‐
705 erable MAILER-DAEMON messages. Additional information on this topic is
706 in the LOCAL_RECIPIENT_README and ADDRESS_CLASS_README documents.
707 show_user_unknown_table_name (yes)
709 Display the name of the recipient table in the "User unknown"
710 responses.
711 canonical_maps (empty)
713 Optional address mapping lookup tables for message headers and
714 envelopes.
715 recipient_canonical_maps (empty)
717 Optional address mapping lookup tables for envelope and header
718 recipient addresses.
719 sender_canonical_maps (empty)
721 Optional address mapping lookup tables for envelope and header
722 sender addresses.
723 Parameters concerning known/unknown local recipients:
725 mydestination ($myhostname, localhost.$mydomain, localhost)
727 The list of domains that are delivered via the $local_transport
728 mail delivery transport.
729 inet_interfaces (all)
731 The network interface addresses that this mail system receives
732 mail on.
733 proxy_interfaces (empty)
735 The network interface addresses that this mail system receives
736 mail on by way of a proxy or network address translation unit.
737 inet_protocols (all)
739 The Internet protocols Postfix will attempt to use when making
740 or accepting connections.
741 local_recipient_maps (proxy:unix:passwd.byname $alias_maps)
743 Lookup tables with all names or addresses of local recipients: a
744 recipient address is local when its domain matches $mydestina‐
745 tion, $inet_interfaces or $proxy_interfaces.
746 unknown_local_recipient_reject_code (550)
748 The numerical Postfix SMTP server response code when a recipient
749 address is local, and $local_recipient_maps specifies a list of
750 lookup tables that does not match the recipient.
751 Parameters concerning known/unknown recipients of relay destinations:
753 relay_domains (Postfix >= 3.0: empty, Postfix < 3.0: $mydestination)
755 What destination domains (and subdomains thereof) this system
756 will relay mail to.
757 relay_recipient_maps (empty)
759 Optional lookup tables with all valid addresses in the domains
760 that match $relay_domains.
761 unknown_relay_recipient_reject_code (550)
763 The numerical Postfix SMTP server reply code when a recipient
764 address matches $relay_domains, and relay_recipient_maps speci‐
765 fies a list of lookup tables that does not match the recipient
766 address.
767 Parameters concerning known/unknown recipients in virtual alias
769 domains:
770 virtual_alias_domains ($virtual_alias_maps)
772 Postfix is final destination for the specified list of virtual
773 alias domains, that is, domains for which all addresses are
774 aliased to addresses in other local or remote domains.
775 virtual_alias_maps ($virtual_maps)
777 Optional lookup tables that alias specific mail addresses or
778 domains to other local or remote address.
779 unknown_virtual_alias_reject_code (550)
781 The Postfix SMTP server reply code when a recipient address
782 matches $virtual_alias_domains, and $virtual_alias_maps speci‐
783 fies a list of lookup tables that does not match the recipient
784 address.
785 Parameters concerning known/unknown recipients in virtual mailbox
787 domains:
788 virtual_mailbox_domains ($virtual_mailbox_maps)
790 Postfix is final destination for the specified list of domains;
791 mail is delivered via the $virtual_transport mail delivery
792 transport.
793 virtual_mailbox_maps (empty)
795 Optional lookup tables with all valid addresses in the domains
796 that match $virtual_mailbox_domains.
797 unknown_virtual_mailbox_reject_code (550)
799 The Postfix SMTP server reply code when a recipient address
800 matches $virtual_mailbox_domains, and $virtual_mailbox_maps
801 specifies a list of lookup tables that does not match the recip‐
802 ient address.
803
805 The following parameters limit resource usage by the SMTP server and/or
806 control client request rates.
807 line_length_limit (2048)
809 Upon input, long lines are chopped up into pieces of at most
810 this length; upon delivery, long lines are reconstructed.
811 queue_minfree (0)
813 The minimal amount of free space in bytes in the queue file sys‐
814 tem that is needed to receive mail.
815 message_size_limit (10240000)
817 The maximal size in bytes of a message, including envelope
818 information.
819 smtpd_recipient_limit (1000)
821 The maximal number of recipients that the Postfix SMTP server
822 accepts per message delivery request.
823 smtpd_timeout (normal: 300s, overload: 10s)
825 The time limit for sending a Postfix SMTP server response and
826 for receiving a remote SMTP client request.
827 smtpd_history_flush_threshold (100)
829 The maximal number of lines in the Postfix SMTP server command
830 history before it is flushed upon receipt of EHLO, RSET, or end
831 of DATA.
832 Available in Postfix version 2.3 and later:
834 smtpd_peername_lookup (yes)
836 Attempt to look up the remote SMTP client hostname, and verify
837 that the name matches the client IP address.
838 The per SMTP client connection count and request rate limits are imple‐
840 mented in co-operation with the anvil(8) service, and are available in
841 Postfix version 2.2 and later.
842 smtpd_client_connection_count_limit (50)
844 How many simultaneous connections any client is allowed to make
845 to this service.
846 smtpd_client_connection_rate_limit (0)
848 The maximal number of connection attempts any client is allowed
849 to make to this service per time unit.
850 smtpd_client_message_rate_limit (0)
852 The maximal number of message delivery requests that any client
853 is allowed to make to this service per time unit, regardless of
854 whether or not Postfix actually accepts those messages.
855 smtpd_client_recipient_rate_limit (0)
857 The maximal number of recipient addresses that any client is
858 allowed to send to this service per time unit, regardless of
859 whether or not Postfix actually accepts those recipients.
860 smtpd_client_event_limit_exceptions ($mynetworks)
862 Clients that are excluded from smtpd_client_*_count/rate_limit
863 restrictions.
864 Available in Postfix version 2.3 and later:
866 smtpd_client_new_tls_session_rate_limit (0)
868 The maximal number of new (i.e., uncached) TLS sessions that a
869 remote SMTP client is allowed to negotiate with this service per
870 time unit.
871 Available in Postfix version 2.9 and later:
873 smtpd_per_record_deadline (normal: no, overload: yes)
875 Change the behavior of the smtpd_timeout and smtpd_start‐
876 tls_timeout time limits, from a time limit per read or write
877 system call, to a time limit to send or receive a complete
878 record (an SMTP command line, SMTP response line, SMTP message
879 content line, or TLS protocol message).
880 Available in Postfix version 3.1 and later:
882 smtpd_client_auth_rate_limit (0)
884 The maximal number of AUTH commands that any client is allowed
885 to send to this service per time unit, regardless of whether or
886 not Postfix actually accepts those commands.
887
889 When a remote SMTP client makes errors, the Postfix SMTP server can
890 insert delays before responding. This can help to slow down run-away
891 software. The behavior is controlled by an error counter that counts
892 the number of errors within an SMTP session that a client makes without
893 delivering mail.
894 smtpd_error_sleep_time (1s)
896 With Postfix version 2.1 and later: the SMTP server response
897 delay after a client has made more than $smtpd_soft_error_limit
898 errors, and fewer than $smtpd_hard_error_limit errors, without
899 delivering mail.
900 smtpd_soft_error_limit (10)
902 The number of errors a remote SMTP client is allowed to make
903 without delivering mail before the Postfix SMTP server slows
904 down all its responses.
905 smtpd_hard_error_limit (normal: 20, overload: 1)
907 The maximal number of errors a remote SMTP client is allowed to
908 make without delivering mail.
909 smtpd_junk_command_limit (normal: 100, overload: 1)
911 The number of junk commands (NOOP, VRFY, ETRN or RSET) that a
912 remote SMTP client can send before the Postfix SMTP server
913 starts to increment the error counter with each junk command.
914 Available in Postfix version 2.1 and later:
916 smtpd_recipient_overshoot_limit (1000)
918 The number of recipients that a remote SMTP client can send in
919 excess of the limit specified with $smtpd_recipient_limit,
920 before the Postfix SMTP server increments the per-session error
921 count for each excess recipient.
922
924 As of version 2.1, Postfix can be configured to delegate access policy
925 decisions to an external server that runs outside Postfix. See the
926 file SMTPD_POLICY_README for more information.
927 smtpd_policy_service_max_idle (300s)
929 The time after which an idle SMTPD policy service connection is
930 closed.
931 smtpd_policy_service_max_ttl (1000s)
933 The time after which an active SMTPD policy service connection
934 is closed.
935 smtpd_policy_service_timeout (100s)
937 The time limit for connecting to, writing to, or receiving from
938 a delegated SMTPD policy server.
939 Available in Postfix version 3.0 and later:
941 smtpd_policy_service_default_action (451 4.3.5 Server configuration
943 problem)
944 The default action when an SMTPD policy service request fails.
945 smtpd_policy_service_request_limit (0)
947 The maximal number of requests per SMTPD policy service connec‐
948 tion, or zero (no limit).
949 smtpd_policy_service_try_limit (2)
951 The maximal number of attempts to send an SMTPD policy service
952 request before giving up.
953 smtpd_policy_service_retry_delay (1s)
955 The delay between attempts to resend a failed SMTPD policy ser‐
956 vice request.
957 Available in Postfix version 3.1 and later:
959 smtpd_policy_service_policy_context (empty)
961 Optional information that the Postfix SMTP server specifies in
962 the "policy_context" attribute of a policy service request
963 (originally, to share the same service endpoint among multiple
964 check_policy_service clients).
965
967 The SMTPD_ACCESS_README document gives an introduction to all the SMTP
968 server access control features.
969 smtpd_delay_reject (yes)
971 Wait until the RCPT TO command before evaluating
972 $smtpd_client_restrictions, $smtpd_helo_restrictions and
973 $smtpd_sender_restrictions, or wait until the ETRN command
974 before evaluating $smtpd_client_restrictions and
975 $smtpd_helo_restrictions.
976 parent_domain_matches_subdomains (see 'postconf -d' output)
978 A list of Postfix features where the pattern "example.com" also
979 matches subdomains of example.com, instead of requiring an
980 explicit ".example.com" pattern.
981 smtpd_client_restrictions (empty)
983 Optional restrictions that the Postfix SMTP server applies in
984 the context of a client connection request.
985 smtpd_helo_required (no)
987 Require that a remote SMTP client introduces itself with the
988 HELO or EHLO command before sending the MAIL command or other
989 commands that require EHLO negotiation.
990 smtpd_helo_restrictions (empty)
992 Optional restrictions that the Postfix SMTP server applies in
993 the context of a client HELO command.
994 smtpd_sender_restrictions (empty)
996 Optional restrictions that the Postfix SMTP server applies in
997 the context of a client MAIL FROM command.
998 smtpd_recipient_restrictions (see 'postconf -d' output)
1000 Optional restrictions that the Postfix SMTP server applies in
1001 the context of a client RCPT TO command, after
1002 smtpd_relay_restrictions.
1003 smtpd_etrn_restrictions (empty)
1005 Optional restrictions that the Postfix SMTP server applies in
1006 the context of a client ETRN command.
1007 allow_untrusted_routing (no)
1009 Forward mail with sender-specified routing
1010 (user[@%!]remote[@%!]site) from untrusted clients to destina‐
1011 tions matching $relay_domains.
1012 smtpd_restriction_classes (empty)
1014 User-defined aliases for groups of access restrictions.
1015 smtpd_null_access_lookup_key (<>)
1017 The lookup key to be used in SMTP access(5) tables instead of
1018 the null sender address.
1019 permit_mx_backup_networks (empty)
1021 Restrict the use of the permit_mx_backup SMTP access feature to
1022 only domains whose primary MX hosts match the listed networks.
1023 Available in Postfix version 2.0 and later:
1025 smtpd_data_restrictions (empty)
1027 Optional access restrictions that the Postfix SMTP server
1028 applies in the context of the SMTP DATA command.
1029 smtpd_expansion_filter (see 'postconf -d' output)
1031 What characters are allowed in $name expansions of RBL reply
1032 templates.
1033 Available in Postfix version 2.1 and later:
1035 smtpd_reject_unlisted_sender (no)
1037 Request that the Postfix SMTP server rejects mail from unknown
1038 sender addresses, even when no explicit reject_unlisted_sender
1039 access restriction is specified.
1040 smtpd_reject_unlisted_recipient (yes)
1042 Request that the Postfix SMTP server rejects mail for unknown
1043 recipient addresses, even when no explicit
1044 reject_unlisted_recipient access restriction is specified.
1045 Available in Postfix version 2.2 and later:
1047 smtpd_end_of_data_restrictions (empty)
1049 Optional access restrictions that the Postfix SMTP server
1050 applies in the context of the SMTP END-OF-DATA command.
1051 Available in Postfix version 2.10 and later:
1053 smtpd_relay_restrictions (permit_mynetworks, permit_sasl_authenticated,
1055 defer_unauth_destination)
1056 Access restrictions for mail relay control that the Postfix SMTP
1057 server applies in the context of the RCPT TO command, before
1058 smtpd_recipient_restrictions.
1059
1061 Postfix version 2.1 introduces sender and recipient address verifica‐
1062 tion. This feature is implemented by sending probe email messages that
1063 are not actually delivered. This feature is requested via the
1064 reject_unverified_sender and reject_unverified_recipient access
1065 restrictions. The status of verification probes is maintained by the
1066 verify(8) server. See the file ADDRESS_VERIFICATION_README for infor‐
1067 mation about how to configure and operate the Postfix sender/recipient
1068 address verification service.
1069 address_verify_poll_count (normal: 3, overload: 1)
1071 How many times to query the verify(8) service for the completion
1072 of an address verification request in progress.
1073 address_verify_poll_delay (3s)
1075 The delay between queries for the completion of an address veri‐
1076 fication request in progress.
1077 address_verify_sender ($double_bounce_sender)
1079 The sender address to use in address verification probes; prior
1080 to Postfix 2.5 the default was "postmaster".
1081 unverified_sender_reject_code (450)
1083 The numerical Postfix SMTP server response code when a recipient
1084 address is rejected by the reject_unverified_sender restriction.
1085 unverified_recipient_reject_code (450)
1087 The numerical Postfix SMTP server response when a recipient
1088 address is rejected by the reject_unverified_recipient restric‐
1089 tion.
1090 Available in Postfix version 2.6 and later:
1092 unverified_sender_defer_code (450)
1094 The numerical Postfix SMTP server response code when a sender
1095 address probe fails due to a temporary error condition.
1096 unverified_recipient_defer_code (450)
1098 The numerical Postfix SMTP server response when a recipient
1099 address probe fails due to a temporary error condition.
1100 unverified_sender_reject_reason (empty)
1102 The Postfix SMTP server's reply when rejecting mail with
1103 reject_unverified_sender.
1104 unverified_recipient_reject_reason (empty)
1106 The Postfix SMTP server's reply when rejecting mail with
1107 reject_unverified_recipient.
1108 unverified_sender_tempfail_action ($reject_tempfail_action)
1110 The Postfix SMTP server's action when reject_unverified_sender
1111 fails due to a temporary error condition.
1112 unverified_recipient_tempfail_action ($reject_tempfail_action)
1114 The Postfix SMTP server's action when reject_unverified_recipi‐
1115 ent fails due to a temporary error condition.
1116 Available with Postfix 2.9 and later:
1118 address_verify_sender_ttl (0s)
1120 The time between changes in the time-dependent portion of
1121 address verification probe sender addresses.
1122
1124 The following parameters control numerical SMTP reply codes and/or text
1125 responses.
1126 access_map_reject_code (554)
1128 The numerical Postfix SMTP server response code for an access(5)
1129 map "reject" action.
1130 defer_code (450)
1132 The numerical Postfix SMTP server response code when a remote
1133 SMTP client request is rejected by the "defer" restriction.
1134 invalid_hostname_reject_code (501)
1136 The numerical Postfix SMTP server response code when the client
1137 HELO or EHLO command parameter is rejected by the
1138 reject_invalid_helo_hostname restriction.
1139 maps_rbl_reject_code (554)
1141 The numerical Postfix SMTP server response code when a remote
1142 SMTP client request is blocked by the reject_rbl_client,
1143 reject_rhsbl_client, reject_rhsbl_reverse_client,
1144 reject_rhsbl_sender or reject_rhsbl_recipient restriction.
1145 non_fqdn_reject_code (504)
1147 The numerical Postfix SMTP server reply code when a client
1148 request is rejected by the reject_non_fqdn_helo_hostname,
1149 reject_non_fqdn_sender or reject_non_fqdn_recipient restriction.
1150 plaintext_reject_code (450)
1152 The numerical Postfix SMTP server response code when a request
1153 is rejected by the reject_plaintext_session restriction.
1154 reject_code (554)
1156 The numerical Postfix SMTP server response code when a remote
1157 SMTP client request is rejected by the "reject" restriction.
1158 relay_domains_reject_code (554)
1160 The numerical Postfix SMTP server response code when a client
1161 request is rejected by the reject_unauth_destination recipient
1162 restriction.
1163 unknown_address_reject_code (450)
1165 The numerical response code when the Postfix SMTP server rejects
1166 a sender or recipient address because its domain is unknown.
1167 unknown_client_reject_code (450)
1169 The numerical Postfix SMTP server response code when a client
1170 without valid address <=> name mapping is rejected by the
1171 reject_unknown_client_hostname restriction.
1172 unknown_hostname_reject_code (450)
1174 The numerical Postfix SMTP server response code when the host‐
1175 name specified with the HELO or EHLO command is rejected by the
1176 reject_unknown_helo_hostname restriction.
1177 Available in Postfix version 2.0 and later:
1179 default_rbl_reply (see 'postconf -d' output)
1181 The default Postfix SMTP server response template for a request
1182 that is rejected by an RBL-based restriction.
1183 multi_recipient_bounce_reject_code (550)
1185 The numerical Postfix SMTP server response code when a remote
1186 SMTP client request is blocked by the reject_multi_recipi‐
1187 ent_bounce restriction.
1188 rbl_reply_maps (empty)
1190 Optional lookup tables with RBL response templates.
1191 Available in Postfix version 2.6 and later:
1193 access_map_defer_code (450)
1195 The numerical Postfix SMTP server response code for an access(5)
1196 map "defer" action, including "defer_if_permit" or
1197 "defer_if_reject".
1198 reject_tempfail_action (defer_if_permit)
1200 The Postfix SMTP server's action when a reject-type restriction
1201 fails due to a temporary error condition.
1202 unknown_helo_hostname_tempfail_action ($reject_tempfail_action)
1204 The Postfix SMTP server's action when reject_unknown_helo_host‐
1205 name fails due to a temporary error condition.
1206 unknown_address_tempfail_action ($reject_tempfail_action)
1208 The Postfix SMTP server's action when
1209 reject_unknown_sender_domain or reject_unknown_recipient_domain
1210 fail due to a temporary error condition.
1211
1213 config_directory (see 'postconf -d' output)
1214 The default location of the Postfix main.cf and master.cf con‐
1215 figuration files.
1216 daemon_timeout (18000s)
1218 How much time a Postfix daemon process may take to handle a
1219 request before it is terminated by a built-in watchdog timer.
1220 command_directory (see 'postconf -d' output)
1222 The location of all postfix administrative commands.
1223 double_bounce_sender (double-bounce)
1225 The sender address of postmaster notifications that are gener‐
1226 ated by the mail system.
1227 ipc_timeout (3600s)
1229 The time limit for sending or receiving information over an
1230 internal communication channel.
1231 mail_name (Postfix)
1233 The mail system name that is displayed in Received: headers, in
1234 the SMTP greeting banner, and in bounced mail.
1235 mail_owner (postfix)
1237 The UNIX system account that owns the Postfix queue and most
1238 Postfix daemon processes.
1239 max_idle (100s)
1241 The maximum amount of time that an idle Postfix daemon process
1242 waits for an incoming connection before terminating voluntarily.
1243 max_use (100)
1245 The maximal number of incoming connections that a Postfix daemon
1246 process will service before terminating voluntarily.
1247 myhostname (see 'postconf -d' output)
1249 The internet hostname of this mail system.
1250 mynetworks (see 'postconf -d' output)
1252 The list of "trusted" remote SMTP clients that have more privi‐
1253 leges than "strangers".
1254 myorigin ($myhostname)
1256 The domain name that locally-posted mail appears to come from,
1257 and that locally posted mail is delivered to.
1258 process_id (read-only)
1260 The process ID of a Postfix command or daemon process.
1261 process_name (read-only)
1263 The process name of a Postfix command or daemon process.
1264 queue_directory (see 'postconf -d' output)
1266 The location of the Postfix top-level queue directory.
1267 recipient_delimiter (empty)
1269 The set of characters that can separate a user name from its
1270 extension (example: user+foo), or a .forward file name from its
1271 extension (example: .forward+foo).
1272 smtpd_banner ($myhostname ESMTP $mail_name)
1274 The text that follows the 220 status code in the SMTP greeting
1275 banner.
1276 syslog_facility (mail)
1278 The syslog facility of Postfix logging.
1279 syslog_name (see 'postconf -d' output)
1281 A prefix that is prepended to the process name in syslog
1282 records, so that, for example, "smtpd" becomes "prefix/smtpd".
1283 Available in Postfix version 2.2 and later:
1285 smtpd_forbidden_commands (CONNECT, GET, POST)
1287 List of commands that cause the Postfix SMTP server to immedi‐
1288 ately terminate the session with a 221 code.
1289 Available in Postfix version 2.5 and later:
1291 smtpd_client_port_logging (no)
1293 Enable logging of the remote SMTP client port in addition to the
1294 hostname and IP address.
1295 Available in Postfix 3.3 and later:
1297 service_name (read-only)
1299 The master.cf service name of a Postfix daemon process.
1300 Available in Postfix 3.4 and later:
1302 smtpd_reject_footer_maps (empty)
1304 Lookup tables, indexed by the complete Postfix SMTP server 4xx
1305 or 5xx response, with reject footer templates.
1306
1308 anvil(8), connection/rate limiting
1309 cleanup(8), message canonicalization
1310 tlsmgr(8), TLS session and PRNG management
1311 trivial-rewrite(8), address resolver
1312 verify(8), address verification service
1313 postconf(5), configuration parameters
1314 master(5), generic daemon options
1315 master(8), process manager
1316 postlogd(8), Postfix logging
1317 syslogd(8), system logging
1318
1320 Use "postconf readme_directory" or "postconf html_directory" to locate
1321 this information.
1322 ADDRESS_CLASS_README, blocking unknown hosted or relay recipients
1323 ADDRESS_REWRITING_README, Postfix address manipulation
1324 BDAT_README, Postfix CHUNKING support
1325 FILTER_README, external after-queue content filter
1326 LOCAL_RECIPIENT_README, blocking unknown local recipients
1327 MILTER_README, before-queue mail filter applications
1328 SMTPD_ACCESS_README, built-in access policies
1329 SMTPD_POLICY_README, external policy server
1330 SMTPD_PROXY_README, external before-queue content filter
1331 SASL_README, Postfix SASL howto
1332 TLS_README, Postfix STARTTLS howto
1333 VERP_README, Postfix XVERP extension
1334 XCLIENT_README, Postfix XCLIENT extension
1335 XFORWARD_README, Postfix XFORWARD extension
1336
1338 The Secure Mailer license must be distributed with this software.
1339
1341 Wietse Venema
1342 IBM T.J. Watson Research
1343 P.O. Box 704
1344 Yorktown Heights, NY 10598, USA
1345 Wietse Venema
1347 Google, Inc.
1348 111 8th Avenue
1349 New York, NY 10011, USA
1350 SASL support originally by:
1352 Till Franke
1353 SuSE Rhein/Main AG
1354 65760 Eschborn, Germany
1355 TLS support originally by:
1357 Lutz Jaenicke
1358 BTU Cottbus
1359 Allgemeine Elektrotechnik
1360 Universitaetsplatz 3-4
1361 D-03044 Cottbus, Germany
1362 Revised TLS support by:
1364 Victor Duchovni
1365 Morgan Stanley
1366 SMTPD(8)