1SMTP(8)                     System Manager's Manual                    SMTP(8)
2
3
4

NAME

6       smtp - Postfix SMTP+LMTP client
7

SYNOPSIS

9       smtp [generic Postfix daemon options]
10

DESCRIPTION

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
18       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
23       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
27       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
31       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
35       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

SMTP DESTINATION SYNTAX

40       SMTP destinations have the following form:
41
42       domainname
43
44       domainname:port
45              Look up the mail exchangers for the specified domain,  and  con‐
46              nect to the specified port (default: smtp).
47
48       [hostname]
49
50       [hostname]:port
51              Look  up  the  address(es) of the specified host, and connect to
52              the specified port (default: smtp).
53
54       [address]
55
56       [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

LMTP DESTINATION SYNTAX

62       LMTP destinations have the following form:
63
64       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
69       inet:hostname
70
71       inet:hostname:port
72
73       inet:[address]
74
75       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

SECURITY

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

STANDARDS

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       RFC 5321 (SMTP protocol)
106

DIAGNOSTICS

108       Problems  and transactions are logged to syslogd(8).  Corrupted message
109       files are marked so that the queue manager can move them to the corrupt
110       queue for further inspection.
111
112       Depending  on the setting of the notify_classes parameter, the postmas‐
113       ter is notified of bounces, protocol problems, and of other trouble.
114

BUGS

116       SMTP and LMTP connection caching does not work with TLS. The  necessary
117       support  for  TLS  object  passivation and re-activation does not exist
118       without closing the session, which defeats the purpose.
119
120       SMTP and LMTP connection caching  assumes  that  SASL  credentials  are
121       valid  for  all  destinations that map onto the same IP address and TCP
122       port.
123

CONFIGURATION PARAMETERS

125       Before Postfix version 2.3, the LMTP client is a separate program  that
126       implements  only  a  subset  of  the functionality available with SMTP:
127       there is no support for TLS, and  connections  are  cached  in-process,
128       making it ineffective when the client is used for multiple domains.
129
130       Most smtp_xxx configuration parameters have an lmtp_xxx "mirror" param‐
131       eter for the equivalent LMTP  feature.  This  document  describes  only
132       those LMTP-related parameters that aren't simply "mirror" parameters.
133
134       Changes  to  main.cf  are picked up automatically, as smtp(8) processes
135       run for only a limited amount of time. Use the command "postfix reload"
136       to speed up a change.
137
138       The  text  below provides only a parameter summary. See postconf(5) for
139       more details including examples.
140

COMPATIBILITY CONTROLS

142       ignore_mx_lookup_error (no)
143              Ignore DNS MX lookups that produce no response.
144
145       smtp_always_send_ehlo (yes)
146              Always send EHLO at the start of an SMTP session.
147
148       smtp_never_send_ehlo (no)
149              Never send EHLO at the start of an SMTP session.
150
151       smtp_defer_if_no_mx_address_found (no)
152              Defer mail delivery when no MX record resolves to an IP address.
153
154       smtp_line_length_limit (998)
155              The maximal length of message header and body lines that Postfix
156              will send via SMTP.
157
158       smtp_pix_workaround_delay_time (10s)
159              How   long   the  Postfix  SMTP  client  pauses  before  sending
160              ".<CR><LF>"  in  order  to  work   around   the   PIX   firewall
161              "<CR><LF>.<CR><LF>" bug.
162
163       smtp_pix_workaround_threshold_time (500s)
164              How long a message must be queued before the Postfix SMTP client
165              turns on the PIX firewall "<CR><LF>.<CR><LF>" bug workaround for
166              delivery through firewalls with "smtp fixup" mode turned on.
167
168       smtp_pix_workarounds (disable_esmtp, delay_dotcrlf)
169              A  list  that  specifies  zero or more workarounds for CISCO PIX
170              firewall bugs.
171
172       smtp_pix_workaround_maps (empty)
173              Lookup tables, indexed by the remote SMTP server  address,  with
174              per-destination workarounds for CISCO PIX firewall bugs.
175
176       smtp_quote_rfc821_envelope (yes)
177              Quote  addresses  in  Postfix  SMTP client MAIL FROM and RCPT TO
178              commands as required by RFC 5321.
179
180       smtp_reply_filter (empty)
181              A mechanism to transform replies from remote  SMTP  servers  one
182              line at a time.
183
184       smtp_skip_5xx_greeting (yes)
185              Skip  remote  SMTP servers that greet with a 5XX status code (go
186              away, do not try again later).
187
188       smtp_skip_quit_response (yes)
189              Do not wait for the response to the SMTP QUIT command.
190
191       Available in Postfix version 2.0 and earlier:
192
193       smtp_skip_4xx_greeting (yes)
194              Skip SMTP servers that greet with a 4XX status  code  (go  away,
195              try again later).
196
197       Available in Postfix version 2.2 and later:
198
199       smtp_discard_ehlo_keyword_address_maps (empty)
200              Lookup  tables,  indexed by the remote SMTP server address, with
201              case insensitive lists of EHLO keywords  (pipelining,  starttls,
202              auth, etc.) that the Postfix SMTP client will ignore in the EHLO
203              response from a remote SMTP server.
204
205       smtp_discard_ehlo_keywords (empty)
206              A case insensitive list of EHLO keywords (pipelining,  starttls,
207              auth, etc.) that the Postfix SMTP client will ignore in the EHLO
208              response from a remote SMTP server.
209
210       smtp_generic_maps (empty)
211              Optional lookup tables that perform  address  rewriting  in  the
212              Postfix  SMTP  client,  typically  to  transform a locally valid
213              address into a globally valid address when sending  mail  across
214              the Internet.
215
216       Available in Postfix version 2.2.9 and later:
217
218       smtp_cname_overrides_servername (version dependent)
219              Allow  DNS  CNAME  records  to  override the servername that the
220              Postfix SMTP client uses for logging, SASL password lookup,  TLS
221              policy decisions, or TLS certificate verification.
222
223       Available in Postfix version 2.3 and later:
224
225       lmtp_discard_lhlo_keyword_address_maps (empty)
226              Lookup  tables,  indexed by the remote LMTP server address, with
227              case insensitive lists of LHLO keywords  (pipelining,  starttls,
228              auth, etc.) that the Postfix LMTP client will ignore in the LHLO
229              response from a remote LMTP server.
230
231       lmtp_discard_lhlo_keywords (empty)
232              A case insensitive list of LHLO keywords (pipelining,  starttls,
233              auth, etc.) that the Postfix LMTP client will ignore in the LHLO
234              response from a remote LMTP server.
235
236       Available in Postfix version 2.4.4 and later:
237
238       send_cyrus_sasl_authzid (no)
239              When authenticating to a remote SMTP or  LMTP  server  with  the
240              default  setting  "no", send no SASL authoriZation ID (authzid);
241              send only the SASL authentiCation ID (authcid)  plus  the  auth‐
242              cid's password.
243
244       Available in Postfix version 2.5 and later:
245
246       smtp_header_checks (empty)
247              Restricted header_checks(5) tables for the Postfix SMTP client.
248
249       smtp_mime_header_checks (empty)
250              Restricted  mime_header_checks(5)  tables  for  the Postfix SMTP
251              client.
252
253       smtp_nested_header_checks (empty)
254              Restricted nested_header_checks(5) tables for the  Postfix  SMTP
255              client.
256
257       smtp_body_checks (empty)
258              Restricted body_checks(5) tables for the Postfix SMTP client.
259
260       Available in Postfix version 2.6 and later:
261
262       tcp_windowsize (0)
263              An  optional  workaround for routers that break TCP window scal‐
264              ing.
265
266       Available in Postfix version 2.8 and later:
267
268       smtp_dns_resolver_options (empty)
269              DNS Resolver options for the Postfix SMTP client.
270
271       Available in Postfix version 2.9 and later:
272
273       smtp_per_record_deadline (no)
274              Change the behavior of the smtp_*_timeout time  limits,  from  a
275              time  limit  per  read  or write system call, to a time limit to
276              send or receive a complete record (an SMTP  command  line,  SMTP
277              response  line,  SMTP message content line, or TLS protocol mes‐
278              sage).
279
280       smtp_send_dummy_mail_auth (no)
281              Whether or not to append the "AUTH=<>" option to the  MAIL  FROM
282              command in SASL-authenticated SMTP sessions.
283

MIME PROCESSING CONTROLS

285       Available in Postfix version 2.0 and later:
286
287       disable_mime_output_conversion (no)
288              Disable the conversion of 8BITMIME format to 7BIT format.
289
290       mime_boundary_length_limit (2048)
291              The maximal length of MIME multipart boundary strings.
292
293       mime_nesting_limit (100)
294              The maximal recursion level that the MIME processor will handle.
295

EXTERNAL CONTENT INSPECTION CONTROLS

297       Available in Postfix version 2.1 and later:
298
299       smtp_send_xforward_command (no)
300              Send  the  non-standard  XFORWARD  command when the Postfix SMTP
301              server EHLO response announces XFORWARD support.
302

SASL AUTHENTICATION CONTROLS

304       smtp_sasl_auth_enable (no)
305              Enable SASL authentication in the Postfix SMTP client.
306
307       smtp_sasl_password_maps (empty)
308              Optional Postfix  SMTP  client  lookup  tables  with  one  user‐
309              name:password  entry  per  remote  hostname or domain, or sender
310              address when sender-dependent authentication is enabled.
311
312       smtp_sasl_security_options (noplaintext, noanonymous)
313              Postfix SMTP client SASL security options; as of Postfix 2.3 the
314              list  of available features depends on the SASL client implemen‐
315              tation that is selected with smtp_sasl_type.
316
317       Available in Postfix version 2.2 and later:
318
319       smtp_sasl_mechanism_filter (empty)
320              If non-empty, a Postfix SMTP client filter for the  remote  SMTP
321              server's list of offered SASL mechanisms.
322
323       Available in Postfix version 2.3 and later:
324
325       smtp_sender_dependent_authentication (no)
326              Enable  sender-dependent  authentication  in  the  Postfix  SMTP
327              client; this is available only  with  SASL  authentication,  and
328              disables  SMTP  connection caching to ensure that mail from dif‐
329              ferent senders will use the appropriate credentials.
330
331       smtp_sasl_path (empty)
332              Implementation-specific information that the Postfix SMTP client
333              passes  through  to  the  SASL  plug-in  implementation  that is
334              selected with smtp_sasl_type.
335
336       smtp_sasl_type (cyrus)
337              The SASL plug-in type that the Postfix SMTP  client  should  use
338              for authentication.
339
340       Available in Postfix version 2.5 and later:
341
342       smtp_sasl_auth_cache_name (empty)
343              An  optional table to prevent repeated SASL authentication fail‐
344              ures with the same remote SMTP  server  hostname,  username  and
345              password.
346
347       smtp_sasl_auth_cache_time (90d)
348              The  maximal age of an smtp_sasl_auth_cache_name entry before it
349              is removed.
350
351       smtp_sasl_auth_soft_bounce (yes)
352              When a remote SMTP server rejects a SASL authentication  request
353              with  a 535 reply code, defer mail delivery instead of returning
354              mail as undeliverable.
355
356       Available in Postfix version 2.9 and later:
357
358       smtp_send_dummy_mail_auth (no)
359              Whether or not to append the "AUTH=<>" option to the  MAIL  FROM
360              command in SASL-authenticated SMTP sessions.
361

STARTTLS SUPPORT CONTROLS

363       Detailed  information  about STARTTLS configuration may be found in the
364       TLS_README document.
365
366       smtp_tls_security_level (empty)
367              The default SMTP TLS security level for the Postfix SMTP client;
368              when a non-empty value is specified, this overrides the obsolete
369              parameters       smtp_use_tls,       smtp_enforce_tls,       and
370              smtp_tls_enforce_peername.
371
372       smtp_sasl_tls_security_options ($smtp_sasl_security_options)
373              The  SASL  authentication security options that the Postfix SMTP
374              client uses for TLS encrypted SMTP sessions.
375
376       smtp_starttls_timeout (300s)
377              Time limit for Postfix SMTP client  write  and  read  operations
378              during TLS startup and shutdown handshake procedures.
379
380       smtp_tls_CAfile (empty)
381              A  file  containing  CA certificates of root CAs trusted to sign
382              either remote SMTP server certificates or intermediate  CA  cer‐
383              tificates.
384
385       smtp_tls_CApath (empty)
386              Directory  with  PEM  format  certificate authority certificates
387              that the Postfix SMTP client uses to verify a remote SMTP server
388              certificate.
389
390       smtp_tls_cert_file (empty)
391              File with the Postfix SMTP client RSA certificate in PEM format.
392
393       smtp_tls_mandatory_ciphers (medium)
394              The  minimum  TLS cipher grade that the Postfix SMTP client will
395              use with mandatory TLS encryption.
396
397       smtp_tls_exclude_ciphers (empty)
398              List of ciphers or cipher types to exclude from the Postfix SMTP
399              client cipher list at all TLS security levels.
400
401       smtp_tls_mandatory_exclude_ciphers (empty)
402              Additional  list  of ciphers or cipher types to exclude from the
403              Postfix SMTP client cipher list at mandatory TLS  security  lev‐
404              els.
405
406       smtp_tls_dcert_file (empty)
407              File with the Postfix SMTP client DSA certificate in PEM format.
408
409       smtp_tls_dkey_file ($smtp_tls_dcert_file)
410              File with the Postfix SMTP client DSA private key in PEM format.
411
412       smtp_tls_key_file ($smtp_tls_cert_file)
413              File with the Postfix SMTP client RSA private key in PEM format.
414
415       smtp_tls_loglevel (0)
416              Enable additional Postfix SMTP client logging of TLS activity.
417
418       smtp_tls_note_starttls_offer (no)
419              Log  the  hostname of a remote SMTP server that offers STARTTLS,
420              when TLS is not already enabled for that server.
421
422       smtp_tls_policy_maps (empty)
423              Optional lookup tables with the Postfix SMTP client TLS security
424              policy by next-hop destination; when a non-empty value is speci‐
425              fied, this overrides the obsolete smtp_tls_per_site parameter.
426
427       smtp_tls_mandatory_protocols (!SSLv2)
428              List of SSL/TLS protocols that the Postfix SMTP client will  use
429              with mandatory TLS encryption.
430
431       smtp_tls_scert_verifydepth (9)
432              The verification depth for remote SMTP server certificates.
433
434       smtp_tls_secure_cert_match (nexthop, dot-nexthop)
435              How  the  Postfix  SMTP  client  verifies the server certificate
436              peername for the "secure" TLS security level.
437
438       smtp_tls_session_cache_database (empty)
439              Name of the file containing the optional Postfix SMTP client TLS
440              session cache.
441
442       smtp_tls_session_cache_timeout (3600s)
443              The  expiration  time  of  Postfix SMTP client TLS session cache
444              information.
445
446       smtp_tls_verify_cert_match (hostname)
447              How the Postfix SMTP  client  verifies  the  server  certificate
448              peername for the "verify" TLS security level.
449
450       tls_daemon_random_bytes (32)
451              The  number  of  pseudo-random bytes that an smtp(8) or smtpd(8)
452              process requests from the tlsmgr(8) server in order to seed  its
453              internal pseudo random number generator (PRNG).
454
455       tls_high_cipherlist (ALL:!EXPORT:!LOW:!MEDIUM:+RC4:@STRENGTH)
456              The OpenSSL cipherlist for "HIGH" grade ciphers.
457
458       tls_medium_cipherlist (ALL:!EXPORT:!LOW:+RC4:@STRENGTH)
459              The OpenSSL cipherlist for "MEDIUM" or higher grade ciphers.
460
461       tls_low_cipherlist (ALL:!EXPORT:+RC4:@STRENGTH)
462              The OpenSSL cipherlist for "LOW" or higher grade ciphers.
463
464       tls_export_cipherlist (ALL:+RC4:@STRENGTH)
465              The OpenSSL cipherlist for "EXPORT" or higher grade ciphers.
466
467       tls_null_cipherlist (eNULL:!aNULL)
468              The  OpenSSL  cipherlist  for  "NULL" grade ciphers that provide
469              authentication without encryption.
470
471       Available in Postfix version 2.4 and later:
472
473       smtp_sasl_tls_verified_security_options           ($smtp_sasl_tls_secu‐
474       rity_options)
475              The  SASL  authentication security options that the Postfix SMTP
476              client uses for TLS encrypted  SMTP  sessions  with  a  verified
477              server certificate.
478
479       Available in Postfix version 2.5 and later:
480
481       smtp_tls_fingerprint_cert_match (empty)
482              List  of  acceptable remote SMTP server certificate fingerprints
483              for  the  "fingerprint"  TLS  security   level   (smtp_tls_secu‐
484              rity_level = fingerprint).
485
486       smtp_tls_fingerprint_digest (md5)
487              The  message  digest  algorithm  used  to  construct remote SMTP
488              server certificate fingerprints.
489
490       Available in Postfix version 2.6 and later:
491
492       smtp_tls_protocols (!SSLv2)
493              List of TLS protocols that the Postfix SMTP client will  exclude
494              or include with opportunistic TLS encryption.
495
496       smtp_tls_ciphers (export)
497              The  minimum  TLS cipher grade that the Postfix SMTP client will
498              use with opportunistic TLS encryption.
499
500       smtp_tls_eccert_file (empty)
501              File with the Postfix SMTP client ECDSA certificate in PEM  for‐
502              mat.
503
504       smtp_tls_eckey_file ($smtp_tls_eccert_file)
505              File  with the Postfix SMTP client ECDSA private key in PEM for‐
506              mat.
507
508       Available in Postfix version 2.7 and later:
509
510       smtp_tls_block_early_mail_reply (no)
511              Try to detect a mail hijacking attack based on  a  TLS  protocol
512              vulnerability  (CVE-2009-3555), where an attacker prepends mali‐
513              cious HELO, MAIL, RCPT, DATA commands to a Postfix  SMTP  client
514              TLS session.
515
516       Available in Postfix version 2.8 and later:
517
518       tls_disable_workarounds (see 'postconf -d' output)
519              List or bit-mask of OpenSSL bug work-arounds to disable.
520

OBSOLETE STARTTLS CONTROLS

522       The  following  configuration  parameters  exist for compatibility with
523       Postfix versions before 2.3. Support for these will  be  removed  in  a
524       future release.
525
526       smtp_use_tls (no)
527              Opportunistic  mode: use TLS when a remote SMTP server announces
528              STARTTLS support, otherwise send the mail in the clear.
529
530       smtp_enforce_tls (no)
531              Enforcement mode: require  that  remote  SMTP  servers  use  TLS
532              encryption, and never send mail in the clear.
533
534       smtp_tls_enforce_peername (yes)
535              With  mandatory  TLS  encryption,  require  that the remote SMTP
536              server hostname matches  the  information  in  the  remote  SMTP
537              server certificate.
538
539       smtp_tls_per_site (empty)
540              Optional  lookup  tables  with the Postfix SMTP client TLS usage
541              policy by next-hop destination and by remote SMTP  server  host‐
542              name.
543
544       smtp_tls_cipherlist (empty)
545              Obsolete  Postfix  < 2.3 control for the Postfix SMTP client TLS
546              cipher list.
547

RESOURCE AND RATE CONTROLS

549       smtp_destination_concurrency_limit        ($default_destination_concur‐
550       rency_limit)
551              The  maximal  number of parallel deliveries to the same destina‐
552              tion via the smtp message delivery transport.
553
554       smtp_destination_recipient_limit ($default_destination_recipient_limit)
555              The maximal number of recipients per message for the  smtp  mes‐
556              sage delivery transport.
557
558       smtp_connect_timeout (30s)
559              The  Postfix SMTP client time limit for completing a TCP connec‐
560              tion, or zero (use the operating system built-in time limit).
561
562       smtp_helo_timeout (300s)
563              The Postfix SMTP client time limit for sending the HELO or  EHLO
564              command,  and  for  receiving  the  initial  remote  SMTP server
565              response.
566
567       lmtp_lhlo_timeout (300s)
568              The Postfix LMTP client time limit for sending the LHLO command,
569              and for receiving the initial remote LMTP server response.
570
571       smtp_xforward_timeout (300s)
572              The Postfix SMTP client time limit for sending the XFORWARD com‐
573              mand, and for receiving the remote SMTP server response.
574
575       smtp_mail_timeout (300s)
576              The Postfix SMTP client time limit for  sending  the  MAIL  FROM
577              command, and for receiving the remote SMTP server response.
578
579       smtp_rcpt_timeout (300s)
580              The  Postfix SMTP client time limit for sending the SMTP RCPT TO
581              command, and for receiving the remote SMTP server response.
582
583       smtp_data_init_timeout (120s)
584              The Postfix SMTP client time limit for  sending  the  SMTP  DATA
585              command, and for receiving the remote SMTP server response.
586
587       smtp_data_xfer_timeout (180s)
588              The  Postfix SMTP client time limit for sending the SMTP message
589              content.
590
591       smtp_data_done_timeout (600s)
592              The Postfix SMTP client time limit for sending the SMTP ".", and
593              for receiving the remote SMTP server response.
594
595       smtp_quit_timeout (300s)
596              The Postfix SMTP client time limit for sending the QUIT command,
597              and for receiving the remote SMTP server response.
598
599       Available in Postfix version 2.1 and later:
600
601       smtp_mx_address_limit (5)
602              The maximal number of MX (mail exchanger) IP addresses that  can
603              result  from Postfix SMTP client mail exchanger lookups, or zero
604              (no limit).
605
606       smtp_mx_session_limit (2)
607              The maximal number of SMTP sessions per delivery request  before
608              the  Postfix  SMTP  client  gives  up or delivers to a fall-back
609              relay host, or zero (no limit).
610
611       smtp_rset_timeout (20s)
612              The Postfix SMTP client time limit for sending the RSET command,
613              and for receiving the remote SMTP server response.
614
615       Available in Postfix version 2.2 and earlier:
616
617       lmtp_cache_connection (yes)
618              Keep  Postfix  LMTP  client connections open for up to $max_idle
619              seconds.
620
621       Available in Postfix version 2.2 and later:
622
623       smtp_connection_cache_destinations (empty)
624              Permanently enable SMTP connection  caching  for  the  specified
625              destinations.
626
627       smtp_connection_cache_on_demand (yes)
628              Temporarily  enable  SMTP connection caching while a destination
629              has a high volume of mail in the active queue.
630
631       smtp_connection_reuse_time_limit (300s)
632              The amount of time during which Postfix will use an SMTP connec‐
633              tion repeatedly.
634
635       smtp_connection_cache_time_limit (2s)
636              When SMTP connection caching is enabled, the amount of time that
637              an unused SMTP client socket is kept open before it is closed.
638
639       Available in Postfix version 2.3 and later:
640
641       connection_cache_protocol_timeout (5s)
642              Time limit for connection cache connect, send or receive  opera‐
643              tions.
644
645       Available in Postfix version 2.9 and later:
646
647       smtp_per_record_deadline (no)
648              Change  the  behavior  of the smtp_*_timeout time limits, from a
649              time limit per read or write system call, to  a  time  limit  to
650              send  or  receive  a complete record (an SMTP command line, SMTP
651              response line, SMTP message content line, or TLS  protocol  mes‐
652              sage).
653

TROUBLE SHOOTING CONTROLS

655       debug_peer_level (2)
656              The  increment  in verbose logging level when a remote client or
657              server matches a pattern in the debug_peer_list parameter.
658
659       debug_peer_list (empty)
660              Optional list of remote client or  server  hostname  or  network
661              address  patterns  that  cause  the  verbose  logging  level  to
662              increase by the amount specified in $debug_peer_level.
663
664       error_notice_recipient (postmaster)
665              The recipient of postmaster notifications  about  mail  delivery
666              problems that are caused by policy, resource, software or proto‐
667              col errors.
668
669       internal_mail_filter_classes (empty)
670              What categories of Postfix-generated mail are subject to before-
671              queue content inspection by non_smtpd_milters, header_checks and
672              body_checks.
673
674       notify_classes (resource, software)
675              The list of error classes that are reported to the postmaster.
676

MISCELLANEOUS CONTROLS

678       best_mx_transport (empty)
679              Where the Postfix  SMTP  client  should  deliver  mail  when  it
680              detects a "mail loops back to myself" error condition.
681
682       config_directory (see 'postconf -d' output)
683              The  default  location of the Postfix main.cf and master.cf con‐
684              figuration files.
685
686       daemon_timeout (18000s)
687              How much time a Postfix daemon process  may  take  to  handle  a
688              request before it is terminated by a built-in watchdog timer.
689
690       delay_logging_resolution_limit (2)
691              The  maximal  number of digits after the decimal point when log‐
692              ging sub-second delay values.
693
694       disable_dns_lookups (no)
695              Disable DNS lookups in the Postfix SMTP and LMTP clients.
696
697       inet_interfaces (all)
698              The network interface addresses that this mail  system  receives
699              mail on.
700
701       inet_protocols (all)
702              The  Internet  protocols Postfix will attempt to use when making
703              or accepting connections.
704
705       ipc_timeout (3600s)
706              The time limit for sending  or  receiving  information  over  an
707              internal communication channel.
708
709       lmtp_assume_final (no)
710              When  a remote LMTP server announces no DSN support, assume that
711              the server performs final delivery, and send "delivered"  deliv‐
712              ery status notifications instead of "relayed".
713
714       lmtp_tcp_port (24)
715              The default TCP port that the Postfix LMTP client connects to.
716
717       max_idle (100s)
718              The  maximum  amount of time that an idle Postfix daemon process
719              waits for an incoming connection before terminating voluntarily.
720
721       max_use (100)
722              The maximal number of incoming connections that a Postfix daemon
723              process will service before terminating voluntarily.
724
725       process_id (read-only)
726              The process ID of a Postfix command or daemon process.
727
728       process_name (read-only)
729              The process name of a Postfix command or daemon process.
730
731       proxy_interfaces (empty)
732              The  network  interface addresses that this mail system receives
733              mail on by way of a proxy or network address translation unit.
734
735       smtp_address_preference (any)
736              The address type ("ipv6", "ipv4" or "any") that the Postfix SMTP
737              client  will  try  first,  when  a destination has IPv6 and IPv4
738              addresses with equal MX preference.
739
740       smtp_bind_address (empty)
741              An optional numerical network  address  that  the  Postfix  SMTP
742              client should bind to when making an IPv4 connection.
743
744       smtp_bind_address6 (empty)
745              An  optional  numerical  network  address  that the Postfix SMTP
746              client should bind to when making an IPv6 connection.
747
748       smtp_helo_name ($myhostname)
749              The hostname to send in the SMTP EHLO or HELO command.
750
751       lmtp_lhlo_name ($myhostname)
752              The hostname to send in the LMTP LHLO command.
753
754       smtp_host_lookup (dns)
755              What mechanisms the Postfix SMTP client uses to look up a host's
756              IP address.
757
758       smtp_randomize_addresses (yes)
759              Randomize the order of equal-preference MX host addresses.
760
761       syslog_facility (mail)
762              The syslog facility of Postfix logging.
763
764       syslog_name (see 'postconf -d' output)
765              The  mail  system  name that is prepended to the process name in
766              syslog records, so that "smtpd"  becomes,  for  example,  "post‐
767              fix/smtpd".
768
769       Available with Postfix 2.2 and earlier:
770
771       fallback_relay (empty)
772              Optional list of relay hosts for SMTP destinations that can't be
773              found or that are unreachable.
774
775       Available with Postfix 2.3 and later:
776
777       smtp_fallback_relay ($fallback_relay)
778              Optional list of relay hosts for SMTP destinations that can't be
779              found or that are unreachable.
780

SEE ALSO

782       generic(5), output address rewriting
783       header_checks(5), message header content inspection
784       body_checks(5), body parts content inspection
785       qmgr(8), queue manager
786       bounce(8), delivery status reports
787       scache(8), connection cache server
788       postconf(5), configuration parameters
789       master(5), generic daemon options
790       master(8), process manager
791       tlsmgr(8), TLS session and PRNG management
792       syslogd(8), system logging
793

README FILES

795       Use  "postconf readme_directory" or "postconf html_directory" to locate
796       this information.
797       SASL_README, Postfix SASL howto
798       TLS_README, Postfix STARTTLS howto
799

LICENSE

801       The Secure Mailer license must be distributed with this software.
802

AUTHOR(S)

804       Wietse Venema
805       IBM T.J. Watson Research
806       P.O. Box 704
807       Yorktown Heights, NY 10598, USA
808
809       Command pipelining in cooperation with:
810       Jon Ribbens
811       Oaktree Internet Solutions Ltd.,
812       Internet House,
813       Canal Basin,
814       Coventry,
815       CV1 4LY, United Kingdom.
816
817       SASL support originally by:
818       Till Franke
819       SuSE Rhein/Main AG
820       65760 Eschborn, Germany
821
822       TLS support originally by:
823       Lutz Jaenicke
824       BTU Cottbus
825       Allgemeine Elektrotechnik
826       Universitaetsplatz 3-4
827       D-03044 Cottbus, Germany
828
829       Revised TLS and SMTP connection cache support by:
830       Victor Duchovni
831       Morgan Stanley
832
833
834
835                                                                       SMTP(8)
Impressum