1SMTP(8) System Manager's Manual SMTP(8)
2
6 smtp - Postfix SMTP+LMTP client
7
9 smtp [generic Postfix daemon options]
10
12 The Postfix SMTP+LMTP client implements the SMTP and LMTP mail delivery
13 protocols. It processes message delivery requests from the queue man‐
14 ager. Each request specifies a queue file, a sender address, a domain
15 or host to deliver to, and recipient information. This program expects
16 to be run from the master(8) process manager.
17 The SMTP+LMTP client updates the queue file and marks recipients as
19 finished, or it informs the queue manager that delivery should be tried
20 again at a later time. Delivery status reports are sent to the
21 bounce(8), defer(8) or trace(8) daemon as appropriate.
22 The SMTP+LMTP client looks up a list of mail exchanger addresses for
24 the destination host, sorts the list by preference, and connects to
25 each listed address until it finds a server that responds.
26 When a server is not reachable, or when mail delivery fails due to a
28 recoverable error condition, the SMTP+LMTP client will try to deliver
29 the mail to an alternate host.
30 After a successful mail transaction, a connection may be saved to the
32 scache(8) connection cache server, so that it may be used by any
33 SMTP+LMTP client for a subsequent transaction.
34 By default, connection caching is enabled temporarily for destinations
36 that have a high volume of mail in the active queue. Connection caching
37 can be enabled permanently for specific destinations.
38
40 SMTP destinations have the following form:
41 domainname
43 domainname:port
45 Look up the mail exchangers for the specified domain, and con‐
46 nect to the specified port (default: smtp).
47 [hostname]
49 [hostname]:port
51 Look up the address(es) of the specified host, and connect to
52 the specified port (default: smtp).
53 [address]
55 [address]:port
57 Connect to the host at the specified address, and connect to the
58 specified port (default: smtp). An IPv6 address must be format‐
59 ted as [ipv6:address].
60
62 LMTP destinations have the following form:
63 unix:pathname
65 Connect to the local UNIX-domain server that is bound to the
66 specified pathname. If the process runs chrooted, an absolute
67 pathname is interpreted relative to the Postfix queue directory.
68 inet:hostname
70 inet:hostname:port
72 inet:[address]
74 inet:[address]:port
76 Connect to the specified TCP port on the specified local or
77 remote host. If no port is specified, connect to the port
78 defined as lmtp in services(4). If no such service is found,
79 the lmtp_tcp_port configuration parameter (default value of 24)
80 will be used. An IPv6 address must be formatted as
81 [ipv6:address].
82
84 The SMTP+LMTP client is moderately security-sensitive. It talks to SMTP
85 or LMTP servers and to DNS servers on the network. The SMTP+LMTP client
86 can be run chrooted at fixed low privilege.
87
89 RFC 821 (SMTP protocol)
90 RFC 822 (ARPA Internet Text Messages)
91 RFC 1651 (SMTP service extensions)
92 RFC 1652 (8bit-MIME transport)
93 RFC 1870 (Message Size Declaration)
94 RFC 2033 (LMTP protocol)
95 RFC 2034 (SMTP Enhanced Error Codes)
96 RFC 2045 (MIME: Format of Internet Message Bodies)
97 RFC 2046 (MIME: Media Types)
98 RFC 2554 (AUTH command)
99 RFC 2821 (SMTP protocol)
100 RFC 2920 (SMTP Pipelining)
101 RFC 3207 (STARTTLS command)
102 RFC 3461 (SMTP DSN Extension)
103 RFC 3463 (Enhanced Status Codes)
104 RFC 4954 (AUTH command)
105
107 Problems and transactions are logged to syslogd(8). Corrupted message
108 files are marked so that the queue manager can move them to the corrupt
109 queue for further inspection.
110 Depending on the setting of the notify_classes parameter, the postmas‐
112 ter is notified of bounces, protocol problems, and of other trouble.
113
115 SMTP and LMTP connection caching does not work with TLS. The necessary
116 support for TLS object passivation and re-activation does not exist
117 without closing the session, which defeats the purpose.
118 SMTP and LMTP connection caching assumes that SASL credentials are
120 valid for all destinations that map onto the same IP address and TCP
121 port.
122
124 Before Postfix version 2.3, the LMTP client is a separate program that
125 implements only a subset of the functionality available with SMTP:
126 there is no support for TLS, and connections are cached in-process,
127 making it ineffective when the client is used for multiple domains.
128 Most smtp_xxx configuration parameters have an lmtp_xxx "mirror" param‐
130 eter for the equivalent LMTP feature. This document describes only
131 those LMTP-related parameters that aren't simply "mirror" parameters.
132 Changes to main.cf are picked up automatically, as smtp(8) processes
134 run for only a limited amount of time. Use the command "postfix reload"
135 to speed up a change.
136 The text below provides only a parameter summary. See postconf(5) for
138 more details including examples.
139
141 ignore_mx_lookup_error (no)
142 Ignore DNS MX lookups that produce no response.
143 smtp_always_send_ehlo (yes)
145 Always send EHLO at the start of an SMTP session.
146 smtp_never_send_ehlo (no)
148 Never send EHLO at the start of an SMTP session.
149 smtp_defer_if_no_mx_address_found (no)
151 Defer mail delivery when no MX record resolves to an IP address.
152 smtp_line_length_limit (990)
154 The maximal length of message header and body lines that Postfix
155 will send via SMTP.
156 smtp_pix_workaround_delay_time (10s)
158 How long the Postfix SMTP client pauses before sending
159 ".<CR><LF>" in order to work around the PIX firewall
160 "<CR><LF>.<CR><LF>" bug.
161 smtp_pix_workaround_threshold_time (500s)
163 How long a message must be queued before the Postfix SMTP client
164 turns on the PIX firewall "<CR><LF>.<CR><LF>" bug workaround for
165 delivery through firewalls with "smtp fixup" mode turned on.
166 smtp_pix_workarounds (disable_esmtp, delay_dotcrlf)
168 A list that specifies zero or more workarounds for CISCO PIX
169 firewall bugs.
170 smtp_pix_workaround_maps (empty)
172 Lookup tables, indexed by the remote SMTP server address, with
173 per-destination workarounds for CISCO PIX firewall bugs.
174 smtp_quote_rfc821_envelope (yes)
176 Quote addresses in SMTP MAIL FROM and RCPT TO commands as
177 required by RFC 2821.
178 smtp_reply_filter (empty)
180 A mechanism to transform replies from remote SMTP servers one
181 line at a time.
182 smtp_skip_5xx_greeting (yes)
184 Skip SMTP servers that greet with a 5XX status code (go away, do
185 not try again later).
186 smtp_skip_quit_response (yes)
188 Do not wait for the response to the SMTP QUIT command.
189 Available in Postfix version 2.0 and earlier:
191 smtp_skip_4xx_greeting (yes)
193 Skip SMTP servers that greet with a 4XX status code (go away,
194 try again later).
195 Available in Postfix version 2.2 and later:
197 smtp_discard_ehlo_keyword_address_maps (empty)
199 Lookup tables, indexed by the remote SMTP server address, with
200 case insensitive lists of EHLO keywords (pipelining, starttls,
201 auth, etc.) that the Postfix SMTP client will ignore in the EHLO
202 response from a remote SMTP server.
203 smtp_discard_ehlo_keywords (empty)
205 A case insensitive list of EHLO keywords (pipelining, starttls,
206 auth, etc.) that the Postfix SMTP client will ignore in the EHLO
207 response from a remote SMTP server.
208 smtp_generic_maps (empty)
210 Optional lookup tables that perform address rewriting in the
211 SMTP client, typically to transform a locally valid address into
212 a globally valid address when sending mail across the Internet.
213 Available in Postfix version 2.2.9 and later:
215 smtp_cname_overrides_servername (version dependent)
217 Allow DNS CNAME records to override the servername that the
218 Postfix SMTP client uses for logging, SASL password lookup, TLS
219 policy decisions, or TLS certificate verification.
220 Available in Postfix version 2.3 and later:
222 lmtp_discard_lhlo_keyword_address_maps (empty)
224 Lookup tables, indexed by the remote LMTP server address, with
225 case insensitive lists of LHLO keywords (pipelining, starttls,
226 auth, etc.) that the LMTP client will ignore in the LHLO
227 response from a remote LMTP server.
228 lmtp_discard_lhlo_keywords (empty)
230 A case insensitive list of LHLO keywords (pipelining, starttls,
231 auth, etc.) that the LMTP client will ignore in the LHLO
232 response from a remote LMTP server.
233 Available in Postfix version 2.4.4 and later:
235 send_cyrus_sasl_authzid (no)
237 When authenticating to a remote SMTP or LMTP server with the
238 default setting "no", send no SASL authoriZation ID (authzid);
239 send only the SASL authentiCation ID (authcid) plus the auth‐
240 cid's password.
241 Available in Postfix version 2.5 and later:
243 smtp_header_checks (empty)
245 Restricted header_checks(5) tables for the Postfix SMTP client.
246 smtp_mime_header_checks (empty)
248 Restricted mime_header_checks(5) tables for the Postfix SMTP
249 client.
250 smtp_nested_header_checks (empty)
252 Restricted nested_header_checks(5) tables for the Postfix SMTP
253 client.
254 smtp_body_checks (empty)
256 Restricted body_checks(5) tables for the Postfix SMTP client.
257 Available in Postfix version 2.6 and later:
259 tcp_windowsize (0)
261 An optional workaround for routers that break TCP window scal‐
262 ing.
263
265 Available in Postfix version 2.0 and later:
266 disable_mime_output_conversion (no)
268 Disable the conversion of 8BITMIME format to 7BIT format.
269 mime_boundary_length_limit (2048)
271 The maximal length of MIME multipart boundary strings.
272 mime_nesting_limit (100)
274 The maximal recursion level that the MIME processor will handle.
275
277 Available in Postfix version 2.1 and later:
278 smtp_send_xforward_command (no)
280 Send the non-standard XFORWARD command when the Postfix SMTP
281 server EHLO response announces XFORWARD support.
282
284 smtp_sasl_auth_enable (no)
285 Enable SASL authentication in the Postfix SMTP client.
286 smtp_sasl_password_maps (empty)
288 Optional SMTP client lookup tables with one username:password
289 entry per remote hostname or domain, or sender address when
290 sender-dependent authentication is enabled.
291 smtp_sasl_security_options (noplaintext, noanonymous)
293 Postfix SMTP client SASL security options; as of Postfix 2.3 the
294 list of available features depends on the SASL client implemen‐
295 tation that is selected with smtp_sasl_type.
296 Available in Postfix version 2.2 and later:
298 smtp_sasl_mechanism_filter (empty)
300 If non-empty, a Postfix SMTP client filter for the remote SMTP
301 server's list of offered SASL mechanisms.
302 Available in Postfix version 2.3 and later:
304 smtp_sender_dependent_authentication (no)
306 Enable sender-dependent authentication in the Postfix SMTP
307 client; this is available only with SASL authentication, and
308 disables SMTP connection caching to ensure that mail from dif‐
309 ferent senders will use the appropriate credentials.
310 smtp_sasl_path (empty)
312 Implementation-specific information that the Postfix SMTP client
313 passes through to the SASL plug-in implementation that is
314 selected with smtp_sasl_type.
315 smtp_sasl_type (cyrus)
317 The SASL plug-in type that the Postfix SMTP client should use
318 for authentication.
319 Available in Postfix version 2.5 and later:
321 smtp_sasl_auth_cache_name (empty)
323 An optional table to prevent repeated SASL authentication fail‐
324 ures with the same remote SMTP server hostname, username and
325 password.
326 smtp_sasl_auth_cache_time (90d)
328 The maximal age of an smtp_sasl_auth_cache_name entry before it
329 is removed.
330 smtp_sasl_auth_soft_bounce (yes)
332 When a remote SMTP server rejects a SASL authentication request
333 with a 535 reply code, defer mail delivery instead of returning
334 mail as undeliverable.
335
337 Detailed information about STARTTLS configuration may be found in the
338 TLS_README document.
339 smtp_tls_security_level (empty)
341 The default SMTP TLS security level for the Postfix SMTP client;
342 when a non-empty value is specified, this overrides the obsolete
343 parameters smtp_use_tls, smtp_enforce_tls, and
344 smtp_tls_enforce_peername.
345 smtp_sasl_tls_security_options ($smtp_sasl_security_options)
347 The SASL authentication security options that the Postfix SMTP
348 client uses for TLS encrypted SMTP sessions.
349 smtp_starttls_timeout (300s)
351 Time limit for Postfix SMTP client write and read operations
352 during TLS startup and shutdown handshake procedures.
353 smtp_tls_CAfile (empty)
355 A file containing CA certificates of root CAs trusted to sign
356 either remote SMTP server certificates or intermediate CA cer‐
357 tificates.
358 smtp_tls_CApath (empty)
360 Directory with PEM format certificate authority certificates
361 that the Postfix SMTP client uses to verify a remote SMTP server
362 certificate.
363 smtp_tls_cert_file (empty)
365 File with the Postfix SMTP client RSA certificate in PEM format.
366 smtp_tls_mandatory_ciphers (medium)
368 The minimum TLS cipher grade that the Postfix SMTP client will
369 use with mandatory TLS encryption.
370 smtp_tls_exclude_ciphers (empty)
372 List of ciphers or cipher types to exclude from the Postfix SMTP
373 client cipher list at all TLS security levels.
374 smtp_tls_mandatory_exclude_ciphers (empty)
376 Additional list of ciphers or cipher types to exclude from the
377 SMTP client cipher list at mandatory TLS security levels.
378 smtp_tls_dcert_file (empty)
380 File with the Postfix SMTP client DSA certificate in PEM format.
381 smtp_tls_dkey_file ($smtp_tls_dcert_file)
383 File with the Postfix SMTP client DSA private key in PEM format.
384 smtp_tls_key_file ($smtp_tls_cert_file)
386 File with the Postfix SMTP client RSA private key in PEM format.
387 smtp_tls_loglevel (0)
389 Enable additional Postfix SMTP client logging of TLS activity.
390 smtp_tls_note_starttls_offer (no)
392 Log the hostname of a remote SMTP server that offers STARTTLS,
393 when TLS is not already enabled for that server.
394 smtp_tls_policy_maps (empty)
396 Optional lookup tables with the Postfix SMTP client TLS security
397 policy by next-hop destination; when a non-empty value is speci‐
398 fied, this overrides the obsolete smtp_tls_per_site parameter.
399 smtp_tls_mandatory_protocols (SSLv3, TLSv1)
401 List of SSL/TLS protocols that the Postfix SMTP client will use
402 with mandatory TLS encryption.
403 smtp_tls_scert_verifydepth (9)
405 The verification depth for remote SMTP server certificates.
406 smtp_tls_secure_cert_match (nexthop, dot-nexthop)
408 The server certificate peername verification method for the
409 "secure" TLS security level.
410 smtp_tls_session_cache_database (empty)
412 Name of the file containing the optional Postfix SMTP client TLS
413 session cache.
414 smtp_tls_session_cache_timeout (3600s)
416 The expiration time of Postfix SMTP client TLS session cache
417 information.
418 smtp_tls_verify_cert_match (hostname)
420 The server certificate peername verification method for the
421 "verify" TLS security level.
422 tls_daemon_random_bytes (32)
424 The number of pseudo-random bytes that an smtp(8) or smtpd(8)
425 process requests from the tlsmgr(8) server in order to seed its
426 internal pseudo random number generator (PRNG).
427 tls_high_cipherlist (ALL:!EXPORT:!LOW:!MEDIUM:+RC4:@STRENGTH)
429 The OpenSSL cipherlist for "HIGH" grade ciphers.
430 tls_medium_cipherlist (ALL:!EXPORT:!LOW:+RC4:@STRENGTH)
432 The OpenSSL cipherlist for "MEDIUM" or higher grade ciphers.
433 tls_low_cipherlist (ALL:!EXPORT:+RC4:@STRENGTH)
435 The OpenSSL cipherlist for "LOW" or higher grade ciphers.
436 tls_export_cipherlist (ALL:+RC4:@STRENGTH)
438 The OpenSSL cipherlist for "EXPORT" or higher grade ciphers.
439 tls_null_cipherlist (eNULL:!aNULL)
441 The OpenSSL cipherlist for "NULL" grade ciphers that provide
442 authentication without encryption.
443 Available in Postfix version 2.4 and later:
445 smtp_sasl_tls_verified_security_options ($smtp_sasl_tls_secu‐
447 rity_options)
448 The SASL authentication security options that the Postfix SMTP
449 client uses for TLS encrypted SMTP sessions with a verified
450 server certificate.
451 Available in Postfix version 2.5 and later:
453 smtp_tls_fingerprint_cert_match (empty)
455 List of acceptable remote SMTP server certificate fingerprints
456 for the "fingerprint" TLS security level (smtp_tls_secu‐
457 rity_level = fingerprint).
458 smtp_tls_fingerprint_digest (md5)
460 The message digest algorithm used to construct remote SMTP
461 server certificate fingerprints.
462 Available in Postfix version 2.6 and later:
464 smtp_tls_protocols (!SSLv2)
466 List of TLS protocols that the Postfix SMTP client will exclude
467 or include with opportunistic TLS encryption.
468 smtp_tls_ciphers (export)
470 The minimum TLS cipher grade that the Postfix SMTP client will
471 use with opportunistic TLS encryption.
472 smtp_tls_eccert_file (empty)
474 File with the Postfix SMTP client ECDSA certificate in PEM for‐
475 mat.
476 smtp_tls_eckey_file ($smtp_tls_eccert_file)
478 File with the Postfix SMTP client ECDSA private key in PEM for‐
479 mat.
480 Available in Postfix version 2.7 and later:
482 smtp_tls_block_early_mail_reply (no)
484 Try to detect a mail hijacking attack based on a TLS protocol
485 vulnerability (CVE-2009-3555), where an attacker prepends mali‐
486 cious HELO, MAIL, RCPT, DATA commands to a Postfix SMTP client
487 TLS session.
488
490 The following configuration parameters exist for compatibility with
491 Postfix versions before 2.3. Support for these will be removed in a
492 future release.
493 smtp_use_tls (no)
495 Opportunistic mode: use TLS when a remote SMTP server announces
496 STARTTLS support, otherwise send the mail in the clear.
497 smtp_enforce_tls (no)
499 Enforcement mode: require that remote SMTP servers use TLS
500 encryption, and never send mail in the clear.
501 smtp_tls_enforce_peername (yes)
503 With mandatory TLS encryption, require that the remote SMTP
504 server hostname matches the information in the remote SMTP
505 server certificate.
506 smtp_tls_per_site (empty)
508 Optional lookup tables with the Postfix SMTP client TLS usage
509 policy by next-hop destination and by remote SMTP server host‐
510 name.
511 smtp_tls_cipherlist (empty)
513 Obsolete Postfix < 2.3 control for the Postfix SMTP client TLS
514 cipher list.
515
517 smtp_destination_concurrency_limit ($default_destination_concur‐
518 rency_limit)
519 The maximal number of parallel deliveries to the same destina‐
520 tion via the smtp message delivery transport.
521 smtp_destination_recipient_limit ($default_destination_recipient_limit)
523 The maximal number of recipients per message for the smtp mes‐
524 sage delivery transport.
525 smtp_connect_timeout (30s)
527 The SMTP client time limit for completing a TCP connection, or
528 zero (use the operating system built-in time limit).
529 smtp_helo_timeout (300s)
531 The SMTP client time limit for sending the HELO or EHLO command,
532 and for receiving the initial server response.
533 lmtp_lhlo_timeout (300s)
535 The LMTP client time limit for sending the LHLO command, and for
536 receiving the initial server response.
537 smtp_xforward_timeout (300s)
539 The SMTP client time limit for sending the XFORWARD command, and
540 for receiving the server response.
541 smtp_mail_timeout (300s)
543 The SMTP client time limit for sending the MAIL FROM command,
544 and for receiving the server response.
545 smtp_rcpt_timeout (300s)
547 The SMTP client time limit for sending the SMTP RCPT TO command,
548 and for receiving the server response.
549 smtp_data_init_timeout (120s)
551 The SMTP client time limit for sending the SMTP DATA command,
552 and for receiving the server response.
553 smtp_data_xfer_timeout (180s)
555 The SMTP client time limit for sending the SMTP message content.
556 smtp_data_done_timeout (600s)
558 The SMTP client time limit for sending the SMTP ".", and for
559 receiving the server response.
560 smtp_quit_timeout (300s)
562 The SMTP client time limit for sending the QUIT command, and for
563 receiving the server response.
564 Available in Postfix version 2.1 and later:
566 smtp_mx_address_limit (5)
568 The maximal number of MX (mail exchanger) IP addresses that can
569 result from mail exchanger lookups, or zero (no limit).
570 smtp_mx_session_limit (2)
572 The maximal number of SMTP sessions per delivery request before
573 giving up or delivering to a fall-back relay host, or zero (no
574 limit).
575 smtp_rset_timeout (20s)
577 The SMTP client time limit for sending the RSET command, and for
578 receiving the server response.
579 Available in Postfix version 2.2 and earlier:
581 lmtp_cache_connection (yes)
583 Keep Postfix LMTP client connections open for up to $max_idle
584 seconds.
585 Available in Postfix version 2.2 and later:
587 smtp_connection_cache_destinations (empty)
589 Permanently enable SMTP connection caching for the specified
590 destinations.
591 smtp_connection_cache_on_demand (yes)
593 Temporarily enable SMTP connection caching while a destination
594 has a high volume of mail in the active queue.
595 smtp_connection_reuse_time_limit (300s)
597 The amount of time during which Postfix will use an SMTP connec‐
598 tion repeatedly.
599 smtp_connection_cache_time_limit (2s)
601 When SMTP connection caching is enabled, the amount of time that
602 an unused SMTP client socket is kept open before it is closed.
603 Available in Postfix version 2.3 and later:
605 connection_cache_protocol_timeout (5s)
607 Time limit for connection cache connect, send or receive opera‐
608 tions.
609
611 debug_peer_level (2)
612 The increment in verbose logging level when a remote client or
613 server matches a pattern in the debug_peer_list parameter.
614 debug_peer_list (empty)
616 Optional list of remote client or server hostname or network
617 address patterns that cause the verbose logging level to
618 increase by the amount specified in $debug_peer_level.
619 error_notice_recipient (postmaster)
621 The recipient of postmaster notifications about mail delivery
622 problems that are caused by policy, resource, software or proto‐
623 col errors.
624 internal_mail_filter_classes (empty)
626 What categories of Postfix-generated mail are subject to before-
627 queue content inspection by non_smtpd_milters, header_checks and
628 body_checks.
629 notify_classes (resource, software)
631 The list of error classes that are reported to the postmaster.
632
634 best_mx_transport (empty)
635 Where the Postfix SMTP client should deliver mail when it
636 detects a "mail loops back to myself" error condition.
637 config_directory (see 'postconf -d' output)
639 The default location of the Postfix main.cf and master.cf con‐
640 figuration files.
641 daemon_timeout (18000s)
643 How much time a Postfix daemon process may take to handle a
644 request before it is terminated by a built-in watchdog timer.
645 delay_logging_resolution_limit (2)
647 The maximal number of digits after the decimal point when log‐
648 ging sub-second delay values.
649 disable_dns_lookups (no)
651 Disable DNS lookups in the Postfix SMTP and LMTP clients.
652 inet_interfaces (all)
654 The network interface addresses that this mail system receives
655 mail on.
656 inet_protocols (ipv4)
658 The Internet protocols Postfix will attempt to use when making
659 or accepting connections.
660 ipc_timeout (3600s)
662 The time limit for sending or receiving information over an
663 internal communication channel.
664 lmtp_assume_final (no)
666 When an LMTP server announces no DSN support, assume that the
667 server performs final delivery, and send "delivered" delivery
668 status notifications instead of "relayed".
669 lmtp_tcp_port (24)
671 The default TCP port that the Postfix LMTP client connects to.
672 max_idle (100s)
674 The maximum amount of time that an idle Postfix daemon process
675 waits for an incoming connection before terminating voluntarily.
676 max_use (100)
678 The maximal number of incoming connections that a Postfix daemon
679 process will service before terminating voluntarily.
680 process_id (read-only)
682 The process ID of a Postfix command or daemon process.
683 process_name (read-only)
685 The process name of a Postfix command or daemon process.
686 proxy_interfaces (empty)
688 The network interface addresses that this mail system receives
689 mail on by way of a proxy or network address translation unit.
690 smtp_bind_address (empty)
692 An optional numerical network address that the Postfix SMTP
693 client should bind to when making an IPv4 connection.
694 smtp_bind_address6 (empty)
696 An optional numerical network address that the Postfix SMTP
697 client should bind to when making an IPv6 connection.
698 smtp_helo_name ($myhostname)
700 The hostname to send in the SMTP EHLO or HELO command.
701 lmtp_lhlo_name ($myhostname)
703 The hostname to send in the LMTP LHLO command.
704 smtp_host_lookup (dns)
706 What mechanisms the Postfix SMTP client uses to look up a host's
707 IP address.
708 smtp_randomize_addresses (yes)
710 Randomize the order of equal-preference MX host addresses.
711 syslog_facility (mail)
713 The syslog facility of Postfix logging.
714 syslog_name (see 'postconf -d' output)
716 The mail system name that is prepended to the process name in
717 syslog records, so that "smtpd" becomes, for example, "post‐
718 fix/smtpd".
719 Available with Postfix 2.2 and earlier:
721 fallback_relay (empty)
723 Optional list of relay hosts for SMTP destinations that can't be
724 found or that are unreachable.
725 Available with Postfix 2.3 and later:
727 smtp_fallback_relay ($fallback_relay)
729 Optional list of relay hosts for SMTP destinations that can't be
730 found or that are unreachable.
731
733 generic(5), output address rewriting
734 header_checks(5), message header content inspection
735 body_checks(5), body parts content inspection
736 qmgr(8), queue manager
737 bounce(8), delivery status reports
738 scache(8), connection cache server
739 postconf(5), configuration parameters
740 master(5), generic daemon options
741 master(8), process manager
742 tlsmgr(8), TLS session and PRNG management
743 syslogd(8), system logging
744
746 Use "postconf readme_directory" or "postconf html_directory" to locate
747 this information.
748 SASL_README, Postfix SASL howto
749 TLS_README, Postfix STARTTLS howto
750
752 The Secure Mailer license must be distributed with this software.
753
755 Wietse Venema
756 IBM T.J. Watson Research
757 P.O. Box 704
758 Yorktown Heights, NY 10598, USA
759 Command pipelining in cooperation with:
761 Jon Ribbens
762 Oaktree Internet Solutions Ltd.,
763 Internet House,
764 Canal Basin,
765 Coventry,
766 CV1 4LY, United Kingdom.
767 SASL support originally by:
769 Till Franke
770 SuSE Rhein/Main AG
771 65760 Eschborn, Germany
772 TLS support originally by:
774 Lutz Jaenicke
775 BTU Cottbus
776 Allgemeine Elektrotechnik
777 Universitaetsplatz 3-4
778 D-03044 Cottbus, Germany
779 Revised TLS and SMTP connection cache support by:
781 Victor Duchovni
782 Morgan Stanley
783 SMTP(8)