summaryrefslogtreecommitdiffstats
path: root/html/smtpd.8.html
blob: 85a8aeebfaa941c82b9e3440dd6782b12e090f42 (plain)
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
61
62
63
64
65
66
67
68
69
70
71
72
73
74
75
76
77
78
79
80
81
82
83
84
85
86
87
88
89
90
91
92
93
94
95
96
97
98
99
100
101
102
103
104
105
106
107
108
109
110
111
112
113
114
115
116
117
118
119
120
121
122
123
124
125
126
127
128
129
130
131
132
133
134
135
136
137
138
139
140
141
142
143
144
145
146
147
148
149
150
151
152
153
154
155
156
157
158
159
160
161
162
163
164
165
166
167
168
169
170
171
172
173
174
175
176
177
178
179
180
181
182
183
184
185
186
187
188
189
190
191
192
193
194
195
196
197
198
199
200
201
202
203
204
205
206
207
208
209
210
211
212
213
214
215
216
217
218
219
220
221
222
223
224
225
226
227
228
229
230
231
232
233
234
235
236
237
238
239
240
241
242
243
244
245
246
247
248
249
250
251
252
253
254
255
256
257
258
259
260
261
262
263
264
265
266
267
268
269
270
271
272
273
274
275
276
277
278
279
280
281
282
283
284
285
286
287
288
289
290
291
292
293
294
295
296
297
298
299
300
301
302
303
304
305
306
307
308
309
310
311
312
313
314
315
316
317
318
319
320
321
322
323
324
325
326
327
328
329
330
331
332
333
334
335
336
337
338
339
340
341
342
343
344
345
346
347
348
349
350
351
352
353
354
355
356
357
358
359
360
361
362
363
364
365
366
367
368
369
370
371
372
373
374
375
376
377
378
379
380
381
382
383
384
385
386
387
388
389
390
391
392
393
394
395
396
397
398
399
400
401
402
403
404
405
406
407
408
409
410
411
412
413
414
415
416
417
418
419
420
421
422
423
424
425
426
427
428
429
430
431
432
433
434
435
436
437
438
439
440
441
442
443
444
445
446
447
448
449
450
451
452
453
454
455
456
457
458
459
460
461
462
463
464
465
466
467
468
469
470
471
472
473
474
475
476
477
478
479
480
481
482
483
484
485
486
487
488
489
490
491
492
493
494
495
496
497
498
499
500
501
502
503
504
505
506
507
508
509
510
511
512
513
514
515
516
517
518
519
520
521
522
523
524
525
526
527
528
529
530
531
532
533
534
535
536
537
538
539
540
541
542
543
544
545
546
547
548
549
550
551
552
553
554
555
556
557
558
559
560
561
562
563
564
565
566
567
568
569
570
571
572
573
574
575
576
577
578
579
580
581
582
583
584
585
586
587
588
589
590
591
592
593
594
595
596
597
598
599
600
601
602
603
604
605
606
607
608
609
610
611
612
613
614
615
616
617
618
619
620
621
622
623
624
625
626
627
628
629
630
631
632
633
634
635
636
637
638
639
640
641
642
643
644
645
646
647
648
649
650
651
652
653
654
655
656
657
658
659
660
661
662
663
664
665
666
667
668
669
670
671
672
673
674
675
676
677
678
679
680
681
682
683
684
685
686
687
688
689
690
691
692
693
694
695
696
697
698
699
700
701
702
703
704
705
706
707
708
709
710
711
712
713
714
715
716
717
718
719
720
721
722
723
724
725
726
727
728
729
730
731
732
733
734
735
736
737
738
739
740
741
742
743
744
745
746
747
748
749
750
751
752
753
754
755
756
757
758
759
760
761
762
763
764
765
766
767
768
769
770
771
772
773
774
775
776
777
778
779
780
781
782
783
784
785
786
787
788
789
790
791
792
793
794
795
796
797
798
799
800
801
802
803
804
805
806
807
808
809
810
811
812
813
814
815
816
817
818
819
820
821
822
823
824
825
826
827
828
829
830
831
832
833
834
835
836
837
838
839
840
841
842
843
844
845
846
847
848
849
850
851
852
853
854
855
856
857
858
859
860
861
862
863
864
865
866
867
868
869
870
871
872
873
874
875
876
877
878
879
880
881
882
883
884
885
886
887
888
889
890
891
892
893
894
895
896
897
898
899
900
901
902
903
904
905
906
907
908
909
910
911
912
913
914
915
916
917
918
919
920
921
922
923
924
925
926
927
928
929
930
931
932
933
934
935
936
937
938
939
940
941
942
943
944
945
946
947
948
949
950
951
952
953
954
955
956
957
958
959
960
961
962
963
964
965
966
967
968
969
970
971
972
973
974
975
976
977
978
979
980
981
982
983
984
985
986
987
988
989
990
991
992
993
994
995
996
997
998
999
1000
1001
1002
1003
1004
1005
1006
1007
1008
1009
1010
1011
1012
1013
1014
1015
1016
1017
1018
1019
1020
1021
1022
1023
1024
1025
1026
1027
1028
1029
1030
1031
1032
1033
1034
1035
1036
1037
1038
1039
1040
1041
1042
1043
1044
1045
1046
1047
1048
1049
1050
1051
1052
1053
1054
1055
1056
1057
1058
1059
1060
1061
1062
1063
1064
1065
1066
1067
1068
1069
1070
1071
1072
1073
1074
1075
1076
1077
1078
1079
1080
1081
1082
1083
1084
1085
1086
1087
1088
1089
1090
1091
1092
1093
1094
1095
1096
1097
1098
1099
1100
1101
1102
1103
1104
1105
1106
1107
1108
1109
1110
1111
1112
1113
1114
1115
1116
1117
1118
1119
1120
1121
1122
1123
1124
1125
1126
1127
1128
1129
1130
1131
1132
1133
1134
1135
1136
1137
1138
1139
1140
1141
1142
1143
1144
1145
1146
1147
1148
1149
1150
1151
1152
1153
1154
1155
1156
1157
1158
1159
1160
1161
1162
1163
1164
1165
1166
1167
1168
1169
1170
1171
1172
1173
1174
1175
1176
1177
1178
1179
1180
1181
1182
1183
1184
1185
1186
1187
1188
1189
1190
1191
1192
1193
1194
1195
1196
1197
1198
1199
1200
1201
1202
1203
1204
1205
1206
1207
1208
1209
1210
1211
1212
1213
1214
1215
1216
1217
1218
1219
1220
1221
1222
1223
1224
1225
1226
1227
1228
1229
1230
1231
1232
1233
1234
1235
1236
1237
1238
1239
1240
1241
1242
1243
1244
1245
1246
1247
1248
1249
1250
1251
1252
1253
1254
1255
1256
1257
1258
1259
1260
1261
1262
1263
1264
1265
1266
1267
1268
1269
1270
1271
1272
1273
1274
1275
1276
1277
1278
1279
1280
1281
1282
1283
1284
1285
1286
1287
1288
1289
1290
1291
1292
1293
1294
1295
1296
1297
1298
1299
1300
1301
1302
1303
1304
1305
1306
1307
1308
1309
1310
1311
1312
1313
1314
1315
1316
1317
1318
1319
1320
1321
1322
1323
1324
1325
1326
1327
1328
1329
1330
1331
1332
1333
1334
1335
1336
1337
1338
1339
1340
1341
1342
1343
1344
1345
1346
1347
1348
1349
1350
1351
1352
1353
1354
1355
1356
1357
1358
1359
1360
1361
1362
1363
1364
1365
1366
1367
1368
1369
1370
1371
1372
1373
1374
1375
1376
1377
1378
1379
1380
1381
1382
1383
1384
1385
1386
1387
1388
1389
1390
1391
1392
1393
1394
1395
1396
1397
1398
1399
1400
1401
1402
1403
1404
1405
1406
1407
1408
1409
1410
1411
1412
1413
1414
1415
1416
1417
1418
1419
1420
1421
1422
1423
1424
1425
1426
1427
1428
1429
1430
1431
1432
1433
1434
1435
1436
1437
1438
1439
1440
1441
1442
1443
1444
1445
1446
1447
1448
1449
1450
1451
1452
1453
1454
1455
1456
1457
1458
1459
1460
1461
1462
1463
1464
1465
1466
1467
1468
1469
1470
1471
1472
1473
1474
1475
1476
1477
1478
1479
1480
1481
1482
1483
1484
1485
1486
1487
1488
1489
1490
1491
<!doctype html public "-//W3C//DTD HTML 4.01 Transitional//EN"
        "http://www.w3.org/TR/html4/loose.dtd">
<html> <head>
<meta http-equiv="Content-Type" content="text/html; charset=utf-8">
<link rel='stylesheet' type='text/css' href='postfix-doc.css'>
<title> Postfix manual - smtpd(8) </title>
</head> <body> <pre>
SMTPD(8)                                                              SMTPD(8)

<b>NAME</b>
       smtpd - Postfix SMTP server

<b>SYNOPSIS</b>
       <b>smtpd</b> [generic Postfix daemon options]

       <b>sendmail -bs</b>

<b>DESCRIPTION</b>
       The  SMTP  server accepts network connection requests and performs zero
       or more SMTP transactions per connection.   Each  received  message  is
       piped  through  the  <a href="cleanup.8.html"><b>cleanup</b>(8)</a> daemon, and is placed into the <b>incoming</b>
       queue as one single queue file.  For this mode of operation,  the  pro-
       gram expects to be run from the <a href="master.8.html"><b>master</b>(8)</a> process manager.

       Alternatively,  the SMTP server be can run in stand-alone mode; this is
       traditionally obtained with "<b>sendmail -bs</b>".  When the SMTP server  runs
       stand-alone  with  non  $<b><a href="postconf.5.html#mail_owner">mail_owner</a></b>  privileges,  it receives mail even
       while the mail system is not running, deposits messages  directly  into
       the  <b>maildrop</b> queue, and disables the SMTP server's access policies. As
       of Postfix version 2.3, the SMTP server refuses to  receive  mail  from
       the network when it runs with non $<b><a href="postconf.5.html#mail_owner">mail_owner</a></b> privileges.

       The  SMTP  server  implements  a  variety  of  policies  for connection
       requests, and for parameters given to <b>HELO, ETRN, MAIL FROM,  VRFY</b>  and
       <b>RCPT TO</b> commands. They are detailed below and in the <a href="postconf.5.html"><b>main.cf</b></a> configura-
       tion file.

<b>SECURITY</b>
       The SMTP server is moderately  security-sensitive.  It  talks  to  SMTP
       clients  and  to DNS servers on the network. The SMTP server can be run
       chrooted at fixed low privilege.

<b>STANDARDS</b>
       <a href="https://tools.ietf.org/html/rfc821">RFC 821</a> (SMTP protocol)
       <a href="https://tools.ietf.org/html/rfc1123">RFC 1123</a> (Host requirements)
       <a href="https://tools.ietf.org/html/rfc1652">RFC 1652</a> (8bit-MIME transport)
       <a href="https://tools.ietf.org/html/rfc1869">RFC 1869</a> (SMTP service extensions)
       <a href="https://tools.ietf.org/html/rfc1870">RFC 1870</a> (Message size declaration)
       <a href="https://tools.ietf.org/html/rfc1985">RFC 1985</a> (ETRN command)
       <a href="https://tools.ietf.org/html/rfc2034">RFC 2034</a> (SMTP enhanced status codes)
       <a href="https://tools.ietf.org/html/rfc2554">RFC 2554</a> (AUTH command)
       <a href="https://tools.ietf.org/html/rfc2821">RFC 2821</a> (SMTP protocol)
       <a href="https://tools.ietf.org/html/rfc2920">RFC 2920</a> (SMTP pipelining)
       <a href="https://tools.ietf.org/html/rfc3030">RFC 3030</a> (CHUNKING without BINARYMIME)
       <a href="https://tools.ietf.org/html/rfc3207">RFC 3207</a> (STARTTLS command)
       <a href="https://tools.ietf.org/html/rfc3461">RFC 3461</a> (SMTP DSN extension)
       <a href="https://tools.ietf.org/html/rfc3463">RFC 3463</a> (Enhanced status codes)
       <a href="https://tools.ietf.org/html/rfc3848">RFC 3848</a> (ESMTP transmission types)
       <a href="https://tools.ietf.org/html/rfc4409">RFC 4409</a> (Message submission)
       <a href="https://tools.ietf.org/html/rfc4954">RFC 4954</a> (AUTH command)
       <a href="https://tools.ietf.org/html/rfc5321">RFC 5321</a> (SMTP protocol)
       <a href="https://tools.ietf.org/html/rfc6531">RFC 6531</a> (Internationalized SMTP)
       <a href="https://tools.ietf.org/html/rfc6533">RFC 6533</a> (Internationalized Delivery Status Notifications)
       <a href="https://tools.ietf.org/html/rfc7505">RFC 7505</a> ("Null MX" No Service Resource Record)

<b>DIAGNOSTICS</b>
       Problems and transactions are logged to <b>syslogd</b>(8) or <a href="postlogd.8.html"><b>postlogd</b>(8)</a>.

       Depending on the setting of the <b><a href="postconf.5.html#notify_classes">notify_classes</a></b> parameter, the  postmas-
       ter  is  notified of bounces, protocol problems, policy violations, and
       of other trouble.

<b>CONFIGURATION PARAMETERS</b>
       Changes to <a href="postconf.5.html"><b>main.cf</b></a> are picked up automatically, as  <a href="smtpd.8.html"><b>smtpd</b>(8)</a>  processes
       run for only a limited amount of time. Use the command "<b>postfix reload</b>"
       to speed up a change.

       The text below provides only a parameter summary. See  <a href="postconf.5.html"><b>postconf</b>(5)</a>  for
       more details including examples.

<b>COMPATIBILITY CONTROLS</b>
       The  following  parameters  work  around implementation errors in other
       software, and/or allow you to override standards in  order  to  prevent
       undesirable use.

       <b><a href="postconf.5.html#broken_sasl_auth_clients">broken_sasl_auth_clients</a> (no)</b>
              Enable  interoperability with remote SMTP clients that implement
              an obsolete version of the AUTH command (<a href="https://tools.ietf.org/html/rfc4954">RFC 4954</a>).

       <b><a href="postconf.5.html#disable_vrfy_command">disable_vrfy_command</a> (no)</b>
              Disable the SMTP VRFY command.

       <b><a href="postconf.5.html#smtpd_noop_commands">smtpd_noop_commands</a> (empty)</b>
              List of commands that the Postfix SMTP server  replies  to  with
              "250  Ok",  without doing any syntax checks and without changing
              state.

       <b><a href="postconf.5.html#strict_rfc821_envelopes">strict_rfc821_envelopes</a> (no)</b>
              Require that addresses received in SMTP MAIL FROM  and  RCPT  TO
              commands  are  enclosed with &lt;&gt;, and that those addresses do not
              contain <a href="https://tools.ietf.org/html/rfc822">RFC 822</a> style comments or phrases.

       Available in Postfix version 2.1 and later:

       <b><a href="postconf.5.html#smtpd_reject_unlisted_sender">smtpd_reject_unlisted_sender</a> (no)</b>
              Request that the Postfix SMTP server rejects mail  from  unknown
              sender  addresses,  even when no explicit <a href="postconf.5.html#reject_unlisted_sender">reject_unlisted_sender</a>
              access restriction is specified.

       <b><a href="postconf.5.html#smtpd_sasl_exceptions_networks">smtpd_sasl_exceptions_networks</a> (empty)</b>
              What remote SMTP clients the Postfix SMTP server will not  offer
              AUTH support to.

       Available in Postfix version 2.2 and later:

       <b><a href="postconf.5.html#smtpd_discard_ehlo_keyword_address_maps">smtpd_discard_ehlo_keyword_address_maps</a> (empty)</b>
              Lookup  tables,  indexed by the remote SMTP client address, with
              case insensitive lists of EHLO keywords  (pipelining,  starttls,
              auth,  etc.)  that  the Postfix SMTP server will not send in the
              EHLO response to a remote SMTP client.

       <b><a href="postconf.5.html#smtpd_discard_ehlo_keywords">smtpd_discard_ehlo_keywords</a> (empty)</b>
              A case insensitive list of EHLO keywords (pipelining,  starttls,
              auth,  etc.)  that  the Postfix SMTP server will not send in the
              EHLO response to a remote SMTP client.

       <b><a href="postconf.5.html#smtpd_delay_open_until_valid_rcpt">smtpd_delay_open_until_valid_rcpt</a> (yes)</b>
              Postpone the start of an SMTP mail  transaction  until  a  valid
              RCPT TO command is received.

       Available in Postfix version 2.3 and later:

       <b><a href="postconf.5.html#smtpd_tls_always_issue_session_ids">smtpd_tls_always_issue_session_ids</a> (yes)</b>
              Force  the  Postfix  SMTP server to issue a TLS session id, even
              when  TLS  session  caching  is   turned   off   (<a href="postconf.5.html#smtpd_tls_session_cache_database">smtpd_tls_ses</a>-
              <a href="postconf.5.html#smtpd_tls_session_cache_database">sion_cache_database</a> is empty).

       Available in Postfix version 2.6 and later:

       <b><a href="postconf.5.html#tcp_windowsize">tcp_windowsize</a> (0)</b>
              An  optional  workaround for routers that break TCP window scal-
              ing.

       Available in Postfix version 2.7 and later:

       <b><a href="postconf.5.html#smtpd_command_filter">smtpd_command_filter</a> (empty)</b>
              A mechanism to transform commands from remote SMTP clients.

       Available in Postfix version 2.9 - 3.6:

       <b><a href="postconf.5.html#smtpd_per_record_deadline">smtpd_per_record_deadline</a> (normal: no, overload: yes)</b>
              Change  the  behavior  of  the  <a href="postconf.5.html#smtpd_timeout">smtpd_timeout</a>  and  <a href="postconf.5.html#smtpd_starttls_timeout">smtpd_start</a>-
              <a href="postconf.5.html#smtpd_starttls_timeout">tls_timeout</a>  time  limits,  from  a time limit per read or write
              system call, to a time limit  to  send  or  receive  a  complete
              record  (an  SMTP command line, SMTP response line, SMTP message
              content line, or TLS protocol message).

       Available in Postfix version 3.0 and later:

       <b><a href="postconf.5.html#smtpd_dns_reply_filter">smtpd_dns_reply_filter</a> (empty)</b>
              Optional filter for Postfix SMTP server DNS lookup results.

       Available in Postfix 3.5 and later:

       <b><a href="postconf.5.html#info_log_address_format">info_log_address_format</a> (external)</b>
              The email address form that will be used  in  non-debug  logging
              (info, warning, etc.).

       Available in Postfix version 3.6 and later:

       <b><a href="postconf.5.html#smtpd_relay_before_recipient_restrictions">smtpd_relay_before_recipient_restrictions</a> (see 'postconf -d' output)</b>
              Evaluate     <a href="postconf.5.html#smtpd_relay_restrictions">smtpd_relay_restrictions</a>    before    <a href="postconf.5.html#smtpd_recipient_restrictions">smtpd_recipi</a>-
              <a href="postconf.5.html#smtpd_recipient_restrictions">ent_restrictions</a>.

       <b><a href="postconf.5.html#known_tcp_ports">known_tcp_ports</a>  (lmtp=24,  smtp=25,   smtps=submissions=465,   submis-</b>
       <b>sion=587)</b>
              Optional setting that avoids lookups in  the  <b>services</b>(5)  data-
              base.

       Available in Postfix version 3.7 and later:

       <b><a href="postconf.5.html#smtpd_per_request_deadline">smtpd_per_request_deadline</a> (normal: no, overload: yes)</b>
              Change  the  behavior  of  the  <a href="postconf.5.html#smtpd_timeout">smtpd_timeout</a>  and  <a href="postconf.5.html#smtpd_starttls_timeout">smtpd_start</a>-
              <a href="postconf.5.html#smtpd_starttls_timeout">tls_timeout</a> time limits, from a time limit per plaintext or  TLS
              read  or  write  call,  to a combined time limit for receiving a
              complete SMTP request and for sending a complete SMTP  response.

       <b><a href="postconf.5.html#smtpd_min_data_rate">smtpd_min_data_rate</a> (500)</b>
              The  minimum  plaintext  data  transfer rate in bytes/second for
              DATA  and  BDAT  requests,  when  deadlines  are  enabled   with
              <a href="postconf.5.html#smtpd_per_request_deadline">smtpd_per_request_deadline</a>.

<b>ADDRESS REWRITING CONTROLS</b>
       See  the <a href="ADDRESS_REWRITING_README.html">ADDRESS_REWRITING_README</a> document for a detailed discussion of
       Postfix address rewriting.

       <b><a href="postconf.5.html#receive_override_options">receive_override_options</a> (empty)</b>
              Enable or disable recipient validation, built-in content filter-
              ing, or address mapping.

       Available in Postfix version 2.2 and later:

       <b><a href="postconf.5.html#local_header_rewrite_clients">local_header_rewrite_clients</a> (<a href="postconf.5.html#permit_inet_interfaces">permit_inet_interfaces</a>)</b>
              Rewrite  or  add  message  headers  in  mail from these clients,
              updating incomplete addresses with the domain name in  $<a href="postconf.5.html#myorigin">myorigin</a>
              or $<a href="postconf.5.html#mydomain">mydomain</a>, and adding missing headers.

<b>BEFORE-SMTPD PROXY AGENT</b>
       Available in Postfix version 2.10 and later:

       <b><a href="postconf.5.html#smtpd_upstream_proxy_protocol">smtpd_upstream_proxy_protocol</a> (empty)</b>
              The  name of the proxy protocol used by an optional before-smtpd
              proxy agent.

       <b><a href="postconf.5.html#smtpd_upstream_proxy_timeout">smtpd_upstream_proxy_timeout</a> (5s)</b>
              The time  limit  for  the  proxy  protocol  specified  with  the
              <a href="postconf.5.html#smtpd_upstream_proxy_protocol">smtpd_upstream_proxy_protocol</a> parameter.

<b>AFTER QUEUE EXTERNAL CONTENT INSPECTION CONTROLS</b>
       As  of  version  1.0,  Postfix can be configured to send new mail to an
       external content filter AFTER the mail is queued. This  content  filter
       is  expected to inject mail back into a (Postfix or other) MTA for fur-
       ther delivery. See the <a href="FILTER_README.html">FILTER_README</a> document for details.

       <b><a href="postconf.5.html#content_filter">content_filter</a> (empty)</b>
              After the message is queued, send  the  entire  message  to  the
              specified <i>transport:destination</i>.

<b>BEFORE QUEUE EXTERNAL CONTENT INSPECTION CONTROLS</b>
       As  of  version  2.1, the Postfix SMTP server can be configured to send
       incoming mail to a real-time SMTP-based content filter BEFORE  mail  is
       queued.  This content filter is expected to inject mail back into Post-
       fix.  See the <a href="SMTPD_PROXY_README.html">SMTPD_PROXY_README</a> document for details on how to config-
       ure and operate this feature.

       <b><a href="postconf.5.html#smtpd_proxy_filter">smtpd_proxy_filter</a> (empty)</b>
              The hostname and TCP port of the mail filtering proxy server.

       <b><a href="postconf.5.html#smtpd_proxy_ehlo">smtpd_proxy_ehlo</a> ($<a href="postconf.5.html#myhostname">myhostname</a>)</b>
              How  the  Postfix SMTP server announces itself to the proxy fil-
              ter.

       <b><a href="postconf.5.html#smtpd_proxy_options">smtpd_proxy_options</a> (empty)</b>
              List of options that control how the Postfix SMTP server  commu-
              nicates with a before-queue content filter.

       <b><a href="postconf.5.html#smtpd_proxy_timeout">smtpd_proxy_timeout</a> (100s)</b>
              The  time limit for connecting to a proxy filter and for sending
              or receiving information.

<b>BEFORE QUEUE MILTER CONTROLS</b>
       As of version 2.3, Postfix supports the Sendmail version 8 Milter (mail
       filter)  protocol.  These content filters run outside Postfix. They can
       inspect the SMTP command  stream  and  the  message  content,  and  can
       request  modifications  before mail is queued. For details see the <a href="MILTER_README.html">MIL</a>-
       <a href="MILTER_README.html">TER_README</a> document.

       <b><a href="postconf.5.html#smtpd_milters">smtpd_milters</a> (empty)</b>
              A list of Milter (mail filter) applications for  new  mail  that
              arrives via the Postfix <a href="smtpd.8.html"><b>smtpd</b>(8)</a> server.

       <b><a href="postconf.5.html#milter_protocol">milter_protocol</a> (6)</b>
              The  mail  filter  protocol version and optional protocol exten-
              sions for communication with  a  Milter  application;  prior  to
              Postfix 2.6 the default protocol is 2.

       <b><a href="postconf.5.html#milter_default_action">milter_default_action</a> (tempfail)</b>
              The  default  action  when  a  Milter  (mail filter) response is
              unavailable (for example, bad Postfix  configuration  or  Milter
              failure).

       <b><a href="postconf.5.html#milter_macro_daemon_name">milter_macro_daemon_name</a> ($<a href="postconf.5.html#myhostname">myhostname</a>)</b>
              The  {daemon_name} macro value for Milter (mail filter) applica-
              tions.

       <b><a href="postconf.5.html#milter_macro_v">milter_macro_v</a> ($<a href="postconf.5.html#mail_name">mail_name</a> $<a href="postconf.5.html#mail_version">mail_version</a>)</b>
              The {v} macro value for Milter (mail filter) applications.

       <b><a href="postconf.5.html#milter_connect_timeout">milter_connect_timeout</a> (30s)</b>
              The time limit for connecting to a Milter (mail filter) applica-
              tion, and for negotiating protocol options.

       <b><a href="postconf.5.html#milter_command_timeout">milter_command_timeout</a> (30s)</b>
              The  time  limit  for  sending an SMTP command to a Milter (mail
              filter) application, and for receiving the response.

       <b><a href="postconf.5.html#milter_content_timeout">milter_content_timeout</a> (300s)</b>
              The time limit for sending message content  to  a  Milter  (mail
              filter) application, and for receiving the response.

       <b><a href="postconf.5.html#milter_connect_macros">milter_connect_macros</a> (see 'postconf -d' output)</b>
              The  macros  that  are sent to Milter (mail filter) applications
              after completion of an SMTP connection.

       <b><a href="postconf.5.html#milter_helo_macros">milter_helo_macros</a> (see 'postconf -d' output)</b>
              The macros that are sent to Milter  (mail  filter)  applications
              after the SMTP HELO or EHLO command.

       <b><a href="postconf.5.html#milter_mail_macros">milter_mail_macros</a> (see 'postconf -d' output)</b>
              The  macros  that  are sent to Milter (mail filter) applications
              after the SMTP MAIL FROM command.

       <b><a href="postconf.5.html#milter_rcpt_macros">milter_rcpt_macros</a> (see 'postconf -d' output)</b>
              The macros that are sent to Milter  (mail  filter)  applications
              after the SMTP RCPT TO command.

       <b><a href="postconf.5.html#milter_data_macros">milter_data_macros</a> (see 'postconf -d' output)</b>
              The  macros  that  are  sent to version 4 or higher Milter (mail
              filter) applications after the SMTP DATA command.

       <b><a href="postconf.5.html#milter_unknown_command_macros">milter_unknown_command_macros</a> (see 'postconf -d' output)</b>
              The macros that are sent to version 3  or  higher  Milter  (mail
              filter) applications after an unknown SMTP command.

       <b><a href="postconf.5.html#milter_end_of_header_macros">milter_end_of_header_macros</a> (see 'postconf -d' output)</b>
              The  macros  that  are sent to Milter (mail filter) applications
              after the end of the message header.

       <b><a href="postconf.5.html#milter_end_of_data_macros">milter_end_of_data_macros</a> (see 'postconf -d' output)</b>
              The macros that are sent to Milter  (mail  filter)  applications
              after the message end-of-data.

       Available in Postfix version 3.1 and later:

       <b><a href="postconf.5.html#milter_macro_defaults">milter_macro_defaults</a> (empty)</b>
              Optional  list  of  <i>name=value</i> pairs that specify default values
              for arbitrary macros that Postfix may send  to  Milter  applica-
              tions.

       Available in Postfix version 3.2 and later:

       <b><a href="postconf.5.html#smtpd_milter_maps">smtpd_milter_maps</a> (empty)</b>
              Lookup  tables  with  Milter  settings per remote SMTP client IP
              address.

<b>GENERAL CONTENT INSPECTION CONTROLS</b>
       The following parameters are applicable for both built-in and  external
       content filters.

       Available in Postfix version 2.1 and later:

       <b><a href="postconf.5.html#receive_override_options">receive_override_options</a> (empty)</b>
              Enable or disable recipient validation, built-in content filter-
              ing, or address mapping.

<b>EXTERNAL CONTENT INSPECTION CONTROLS</b>
       The following parameters  are  applicable  for  both  before-queue  and
       after-queue content filtering.

       Available in Postfix version 2.1 and later:

       <b><a href="postconf.5.html#smtpd_authorized_xforward_hosts">smtpd_authorized_xforward_hosts</a> (empty)</b>
              What  remote  SMTP  clients are allowed to use the XFORWARD fea-
              ture.

<b>SASL AUTHENTICATION CONTROLS</b>
       Postfix SASL support (<a href="https://tools.ietf.org/html/rfc4954">RFC 4954</a>) can be used to authenticate remote SMTP
       clients  to  the  Postfix  SMTP server, and to authenticate the Postfix
       SMTP client to a remote SMTP server.  See the <a href="SASL_README.html">SASL_README</a> document  for
       details.

       <b><a href="postconf.5.html#broken_sasl_auth_clients">broken_sasl_auth_clients</a> (no)</b>
              Enable  interoperability with remote SMTP clients that implement
              an obsolete version of the AUTH command (<a href="https://tools.ietf.org/html/rfc4954">RFC 4954</a>).

       <b><a href="postconf.5.html#smtpd_sasl_auth_enable">smtpd_sasl_auth_enable</a> (no)</b>
              Enable SASL authentication in the Postfix SMTP server.

       <b><a href="postconf.5.html#smtpd_sasl_local_domain">smtpd_sasl_local_domain</a> (empty)</b>
              The name of the Postfix SMTP server's local SASL  authentication
              realm.

       <b><a href="postconf.5.html#smtpd_sasl_security_options">smtpd_sasl_security_options</a> (noanonymous)</b>
              Postfix SMTP server SASL security options; as of Postfix 2.3 the
              list of available features depends on the SASL server  implemen-
              tation that is selected with <b><a href="postconf.5.html#smtpd_sasl_type">smtpd_sasl_type</a></b>.

       <b><a href="postconf.5.html#smtpd_sender_login_maps">smtpd_sender_login_maps</a> (empty)</b>
              Optional  lookup  table  with  the SASL login names that own the
              sender (MAIL FROM) addresses.

       Available in Postfix version 2.1 and later:

       <b><a href="postconf.5.html#smtpd_sasl_exceptions_networks">smtpd_sasl_exceptions_networks</a> (empty)</b>
              What remote SMTP clients the Postfix SMTP server will not  offer
              AUTH support to.

       Available in Postfix version 2.1 and 2.2:

       <b><a href="postconf.5.html#smtpd_sasl_application_name">smtpd_sasl_application_name</a> (smtpd)</b>
              The  application name that the Postfix SMTP server uses for SASL
              server initialization.

       Available in Postfix version 2.3 and later:

       <b><a href="postconf.5.html#smtpd_sasl_authenticated_header">smtpd_sasl_authenticated_header</a> (no)</b>
              Report the SASL authenticated user name in the <a href="smtpd.8.html"><b>smtpd</b>(8)</a> Received
              message header.

       <b><a href="postconf.5.html#smtpd_sasl_path">smtpd_sasl_path</a> (smtpd)</b>
              Implementation-specific information that the Postfix SMTP server
              passes through  to  the  SASL  plug-in  implementation  that  is
              selected with <b><a href="postconf.5.html#smtpd_sasl_type">smtpd_sasl_type</a></b>.

       <b><a href="postconf.5.html#smtpd_sasl_type">smtpd_sasl_type</a> (cyrus)</b>
              The  SASL  plug-in  type that the Postfix SMTP server should use
              for authentication.

       Available in Postfix version 2.5 and later:

       <b><a href="postconf.5.html#cyrus_sasl_config_path">cyrus_sasl_config_path</a> (empty)</b>
              Search path for Cyrus SASL application configuration files, cur-
              rently used only to locate the $<a href="postconf.5.html#smtpd_sasl_path">smtpd_sasl_path</a>.conf file.

       Available in Postfix version 2.11 and later:

       <b><a href="postconf.5.html#smtpd_sasl_service">smtpd_sasl_service</a> (smtp)</b>
              The  service  name  that  is  passed to the SASL plug-in that is
              selected with <b><a href="postconf.5.html#smtpd_sasl_type">smtpd_sasl_type</a></b> and <b><a href="postconf.5.html#smtpd_sasl_path">smtpd_sasl_path</a></b>.

       Available in Postfix version 3.4 and later:

       <b><a href="postconf.5.html#smtpd_sasl_response_limit">smtpd_sasl_response_limit</a> (12288)</b>
              The maximum length of a SASL client's response to a server chal-
              lenge.

       Available in Postfix 3.6 and later:

       <b><a href="postconf.5.html#smtpd_sasl_mechanism_filter">smtpd_sasl_mechanism_filter</a> (!external, <a href="DATABASE_README.html#types">static</a>:rest)</b>
              If  non-empty,  a  filter  for the SASL mechanism names that the
              Postfix SMTP server will announce in the EHLO response.

<b>STARTTLS SUPPORT CONTROLS</b>
       Detailed information about STARTTLS configuration may be found  in  the
       <a href="TLS_README.html">TLS_README</a> document.

       <b><a href="postconf.5.html#smtpd_tls_security_level">smtpd_tls_security_level</a> (empty)</b>
              The  SMTP TLS security level for the Postfix SMTP server; when a
              non-empty value is specified, this overrides the obsolete param-
              eters <a href="postconf.5.html#smtpd_use_tls">smtpd_use_tls</a> and <a href="postconf.5.html#smtpd_enforce_tls">smtpd_enforce_tls</a>.

       <b><a href="postconf.5.html#smtpd_sasl_tls_security_options">smtpd_sasl_tls_security_options</a> ($<a href="postconf.5.html#smtpd_sasl_security_options">smtpd_sasl_security_options</a>)</b>
              The  SASL  authentication security options that the Postfix SMTP
              server uses for TLS encrypted SMTP sessions.

       <b><a href="postconf.5.html#smtpd_starttls_timeout">smtpd_starttls_timeout</a> (see 'postconf -d' output)</b>
              The time limit for Postfix SMTP server write and read operations
              during TLS startup and shutdown handshake procedures.

       <b><a href="postconf.5.html#smtpd_tls_CAfile">smtpd_tls_CAfile</a> (empty)</b>
              A  file  containing  (PEM  format)  CA  certificates of root CAs
              trusted to sign either remote SMTP client certificates or inter-
              mediate CA certificates.

       <b><a href="postconf.5.html#smtpd_tls_CApath">smtpd_tls_CApath</a> (empty)</b>
              A  directory containing (PEM format) CA certificates of root CAs
              trusted to sign either remote SMTP client certificates or inter-
              mediate CA certificates.

       <b><a href="postconf.5.html#smtpd_tls_always_issue_session_ids">smtpd_tls_always_issue_session_ids</a> (yes)</b>
              Force  the  Postfix  SMTP server to issue a TLS session id, even
              when  TLS  session  caching  is   turned   off   (<a href="postconf.5.html#smtpd_tls_session_cache_database">smtpd_tls_ses</a>-
              <a href="postconf.5.html#smtpd_tls_session_cache_database">sion_cache_database</a> is empty).

       <b><a href="postconf.5.html#smtpd_tls_ask_ccert">smtpd_tls_ask_ccert</a> (no)</b>
              Ask a remote SMTP client for a client certificate.

       <b><a href="postconf.5.html#smtpd_tls_auth_only">smtpd_tls_auth_only</a> (no)</b>
              When  TLS  encryption is optional in the Postfix SMTP server, do
              not announce or accept SASL authentication over unencrypted con-
              nections.

       <b><a href="postconf.5.html#smtpd_tls_ccert_verifydepth">smtpd_tls_ccert_verifydepth</a> (9)</b>
              The verification depth for remote SMTP client certificates.

       <b><a href="postconf.5.html#smtpd_tls_cert_file">smtpd_tls_cert_file</a> (empty)</b>
              File with the Postfix SMTP server RSA certificate in PEM format.

       <b><a href="postconf.5.html#smtpd_tls_exclude_ciphers">smtpd_tls_exclude_ciphers</a> (empty)</b>
              List of ciphers or cipher types to exclude from the SMTP  server
              cipher list at all TLS security levels.

       <b><a href="postconf.5.html#smtpd_tls_dcert_file">smtpd_tls_dcert_file</a> (empty)</b>
              File with the Postfix SMTP server DSA certificate in PEM format.

       <b><a href="postconf.5.html#smtpd_tls_dh1024_param_file">smtpd_tls_dh1024_param_file</a> (empty)</b>
              File with DH parameters that the Postfix SMTP server should  use
              with non-export EDH ciphers.

       <b><a href="postconf.5.html#smtpd_tls_dh512_param_file">smtpd_tls_dh512_param_file</a> (empty)</b>
              File  with DH parameters that the Postfix SMTP server should use
              with export-grade EDH ciphers.

       <b><a href="postconf.5.html#smtpd_tls_dkey_file">smtpd_tls_dkey_file</a> ($<a href="postconf.5.html#smtpd_tls_dcert_file">smtpd_tls_dcert_file</a>)</b>
              File with the Postfix SMTP server DSA private key in PEM format.

       <b><a href="postconf.5.html#smtpd_tls_key_file">smtpd_tls_key_file</a> ($<a href="postconf.5.html#smtpd_tls_cert_file">smtpd_tls_cert_file</a>)</b>
              File with the Postfix SMTP server RSA private key in PEM format.

       <b><a href="postconf.5.html#smtpd_tls_loglevel">smtpd_tls_loglevel</a> (0)</b>
              Enable additional Postfix SMTP server logging of TLS activity.

       <b><a href="postconf.5.html#smtpd_tls_mandatory_ciphers">smtpd_tls_mandatory_ciphers</a> (medium)</b>
              The minimum TLS cipher grade that the Postfix SMTP  server  will
              use with mandatory TLS encryption.

       <b><a href="postconf.5.html#smtpd_tls_mandatory_exclude_ciphers">smtpd_tls_mandatory_exclude_ciphers</a> (empty)</b>
              Additional  list  of ciphers or cipher types to exclude from the
              Postfix SMTP server cipher list at mandatory TLS  security  lev-
              els.

       <b><a href="postconf.5.html#smtpd_tls_mandatory_protocols">smtpd_tls_mandatory_protocols</a> (see 'postconf -d' output)</b>
              TLS protocols accepted by the Postfix SMTP server with mandatory
              TLS encryption.

       <b><a href="postconf.5.html#smtpd_tls_received_header">smtpd_tls_received_header</a> (no)</b>
              Request that the Postfix SMTP server produces Received:  message
              headers  that  include information about the protocol and cipher
              used, as well as the remote SMTP client  CommonName  and  client
              certificate issuer CommonName.

       <b><a href="postconf.5.html#smtpd_tls_req_ccert">smtpd_tls_req_ccert</a> (no)</b>
              With  mandatory  TLS  encryption,  require a trusted remote SMTP
              client certificate in order to allow TLS connections to proceed.

       <b><a href="postconf.5.html#smtpd_tls_wrappermode">smtpd_tls_wrappermode</a> (no)</b>
              Run  the  Postfix  SMTP server in TLS "wrapper" mode, instead of
              using the STARTTLS command.

       <b><a href="postconf.5.html#tls_daemon_random_bytes">tls_daemon_random_bytes</a> (32)</b>
              The number of pseudo-random bytes that an  <a href="smtp.8.html"><b>smtp</b>(8)</a>  or  <a href="smtpd.8.html"><b>smtpd</b>(8)</a>
              process  requests from the <a href="tlsmgr.8.html"><b>tlsmgr</b>(8)</a> server in order to seed its
              internal pseudo random number generator (PRNG).

       <b><a href="postconf.5.html#tls_high_cipherlist">tls_high_cipherlist</a> (see 'postconf -d' output)</b>
              The OpenSSL cipherlist for "high" grade ciphers.

       <b><a href="postconf.5.html#tls_medium_cipherlist">tls_medium_cipherlist</a> (see 'postconf -d' output)</b>
              The OpenSSL cipherlist for "medium" or higher grade ciphers.

       <b><a href="postconf.5.html#tls_null_cipherlist">tls_null_cipherlist</a> (eNULL:!aNULL)</b>
              The OpenSSL cipherlist for "NULL"  grade  ciphers  that  provide
              authentication without encryption.

       Available in Postfix version 2.3..3.7:

       <b><a href="postconf.5.html#tls_low_cipherlist">tls_low_cipherlist</a> (see 'postconf -d' output)</b>
              The OpenSSL cipherlist for "low" or higher grade ciphers.

       <b><a href="postconf.5.html#tls_export_cipherlist">tls_export_cipherlist</a> (see 'postconf -d' output)</b>
              The OpenSSL cipherlist for "export" or higher grade ciphers.

       Available in Postfix version 2.5 and later:

       <b><a href="postconf.5.html#smtpd_tls_fingerprint_digest">smtpd_tls_fingerprint_digest</a> (see 'postconf -d' output)</b>
              The   message   digest   algorithm   to  construct  remote  SMTP
              client-certificate  fingerprints  or  public  key   fingerprints
              (Postfix   2.9   and  later)  for  <b><a href="postconf.5.html#check_ccert_access">check_ccert_access</a></b>  and  <b>per-</b>
              <b>mit_tls_clientcerts</b>.

       Available in Postfix version 2.6 and later:

       <b><a href="postconf.5.html#smtpd_tls_protocols">smtpd_tls_protocols</a> (see 'postconf -d' output)</b>
              TLS protocols accepted by the Postfix SMTP  server  with  oppor-
              tunistic TLS encryption.

       <b><a href="postconf.5.html#smtpd_tls_ciphers">smtpd_tls_ciphers</a> (medium)</b>
              The  minimum  TLS cipher grade that the Postfix SMTP server will
              use with opportunistic TLS encryption.

       <b><a href="postconf.5.html#smtpd_tls_eccert_file">smtpd_tls_eccert_file</a> (empty)</b>
              File with the Postfix SMTP server ECDSA certificate in PEM  for-
              mat.

       <b><a href="postconf.5.html#smtpd_tls_eckey_file">smtpd_tls_eckey_file</a> ($<a href="postconf.5.html#smtpd_tls_eccert_file">smtpd_tls_eccert_file</a>)</b>
              File  with the Postfix SMTP server ECDSA private key in PEM for-
              mat.

       <b><a href="postconf.5.html#smtpd_tls_eecdh_grade">smtpd_tls_eecdh_grade</a> (see 'postconf -d' output)</b>
              The Postfix SMTP server  security  grade  for  ephemeral  ellip-
              tic-curve Diffie-Hellman (EECDH) key exchange.

       <b><a href="postconf.5.html#tls_eecdh_strong_curve">tls_eecdh_strong_curve</a> (prime256v1)</b>
              The  elliptic curve used by the Postfix SMTP server for sensibly
              strong ephemeral ECDH key exchange.

       <b><a href="postconf.5.html#tls_eecdh_ultra_curve">tls_eecdh_ultra_curve</a> (secp384r1)</b>
              The elliptic curve used by the Postfix SMTP server for maximally
              strong ephemeral ECDH key exchange.

       Available in Postfix version 2.8 and later:

       <b><a href="postconf.5.html#tls_preempt_cipherlist">tls_preempt_cipherlist</a> (no)</b>
              With SSLv3 and later, use the Postfix SMTP server's cipher pref-
              erence order instead of the remote  client's  cipher  preference
              order.

       <b><a href="postconf.5.html#tls_disable_workarounds">tls_disable_workarounds</a> (see 'postconf -d' output)</b>
              List or bit-mask of OpenSSL bug work-arounds to disable.

       Available in Postfix version 2.11 and later:

       <b><a href="postconf.5.html#tlsmgr_service_name">tlsmgr_service_name</a> (tlsmgr)</b>
              The name of the <a href="tlsmgr.8.html"><b>tlsmgr</b>(8)</a> service entry in <a href="master.5.html">master.cf</a>.

       Available in Postfix version 3.0 and later:

       <b><a href="postconf.5.html#tls_session_ticket_cipher">tls_session_ticket_cipher</a>  (Postfix</b> &gt;<b>= 3.0: aes-256-cbc, Postfix</b> &lt; <b>3.0:</b>
       <b>aes-128-cbc)</b>
              Algorithm used to encrypt <a href="https://tools.ietf.org/html/rfc5077">RFC5077</a> TLS session tickets.

       Available in Postfix version 3.2 and later:

       <b><a href="postconf.5.html#tls_eecdh_auto_curves">tls_eecdh_auto_curves</a> (see 'postconf -d' output)</b>
              The prioritized list of elliptic curves supported by the Postfix
              SMTP client and server.

       Available in Postfix version 3.4 and later:

       <b><a href="postconf.5.html#smtpd_tls_chain_files">smtpd_tls_chain_files</a> (empty)</b>
              List of one or more PEM files, each holding one or more  private
              keys directly followed by a corresponding certificate chain.

       <b><a href="postconf.5.html#tls_server_sni_maps">tls_server_sni_maps</a> (empty)</b>
              Optional  lookup tables that map names received from remote SMTP
              clients via the TLS Server Name Indication  (SNI)  extension  to
              the appropriate keys and certificate chains.

       Available in Postfix 3.5, 3.4.6, 3.3.5, 3.2.10, 3.1.13 and later:

       <b><a href="postconf.5.html#tls_fast_shutdown_enable">tls_fast_shutdown_enable</a> (yes)</b>
              A  workaround  for implementations that hang Postfix while shut-
              ting down a TLS session, until Postfix times out.

       Available in Postfix version 3.8 and later:

       <b><a href="postconf.5.html#tls_ffdhe_auto_groups">tls_ffdhe_auto_groups</a> (see 'postconf -d' output)</b>
              The prioritized list of  finite-field  Diffie-Hellman  ephemeral
              (FFDHE) key exchange groups supported by the Postfix SMTP client
              and server.

       Available in Postfix 3.9, 3.8.1, 3.7.6, 3.6.10, 3.5.20 and later:

       <b><a href="postconf.5.html#tls_config_file">tls_config_file</a> (default)</b>
              Optional configuration file with baseline OpenSSL settings.

       <b><a href="postconf.5.html#tls_config_name">tls_config_name</a> (empty)</b>
              The application name passed by Postfix to OpenSSL  library  ini-
              tialization functions.

       Available in Postfix version 3.9 and later:

       <b><a href="postconf.5.html#smtpd_tls_enable_rpk">smtpd_tls_enable_rpk</a> (no)</b>
              Request  that remote SMTP clients send an <a href="https://tools.ietf.org/html/rfc7250">RFC7250</a> raw public key
              instead of an X.509 certificate, when asking  for  or  requiring
              client authentication.

<b>OBSOLETE STARTTLS CONTROLS</b>
       The  following  configuration  parameters  exist for compatibility with
       Postfix versions before 2.3. Support for these will  be  removed  in  a
       future release.

       <b><a href="postconf.5.html#smtpd_use_tls">smtpd_use_tls</a> (no)</b>
              Opportunistic  TLS:  announce  STARTTLS  support  to remote SMTP
              clients, but do not require that clients use TLS encryption.

       <b><a href="postconf.5.html#smtpd_enforce_tls">smtpd_enforce_tls</a> (no)</b>
              Mandatory TLS: announce STARTTLS support to remote SMTP clients,
              and require that clients use TLS encryption.

       <b><a href="postconf.5.html#smtpd_tls_cipherlist">smtpd_tls_cipherlist</a> (empty)</b>
              Obsolete  Postfix  &lt; 2.3 control for the Postfix SMTP server TLS
              cipher list.

<b>SMTPUTF8 CONTROLS</b>
       Preliminary SMTPUTF8 support is introduced with Postfix 3.0.

       <b><a href="postconf.5.html#smtputf8_enable">smtputf8_enable</a> (yes)</b>
              Enable preliminary SMTPUTF8 support for the protocols  described
              in <a href="https://tools.ietf.org/html/rfc6531">RFC 6531</a>, <a href="https://tools.ietf.org/html/rfc6532">RFC 6532</a>, and <a href="https://tools.ietf.org/html/rfc6533">RFC 6533</a>.

       <b><a href="postconf.5.html#strict_smtputf8">strict_smtputf8</a> (no)</b>
              Enable stricter enforcement of the SMTPUTF8 protocol.

       <b><a href="postconf.5.html#smtputf8_autodetect_classes">smtputf8_autodetect_classes</a> (sendmail, verify)</b>
              Detect  that  a message requires SMTPUTF8 support for the speci-
              fied mail origin classes.

       Available in Postfix version 3.2 and later:

       <b><a href="postconf.5.html#enable_idna2003_compatibility">enable_idna2003_compatibility</a> (no)</b>
              Enable  'transitional'  compatibility   between   IDNA2003   and
              IDNA2008,  when  converting UTF-8 domain names to/from the ASCII
              form that is used for DNS lookups.

<b>VERP SUPPORT CONTROLS</b>
       With VERP style delivery, each recipient of a message receives  a  cus-
       tomized  copy of the message with his/her own recipient address encoded
       in the envelope sender address.  The <a href="VERP_README.html">VERP_README</a> file describes config-
       uration  and operation details of Postfix support for variable envelope
       return path addresses.  VERP style delivery is requested with the  SMTP
       XVERP  command  or  with  the  "sendmail -V" command-line option and is
       available in Postfix version 1.1 and later.

       <b><a href="postconf.5.html#default_verp_delimiters">default_verp_delimiters</a> (+=)</b>
              The two default VERP delimiter characters.

       <b><a href="postconf.5.html#verp_delimiter_filter">verp_delimiter_filter</a> (-=+)</b>
              The characters Postfix accepts as VERP delimiter  characters  on
              the Postfix <a href="sendmail.1.html"><b>sendmail</b>(1)</a> command line and in SMTP commands.

       Available in Postfix version 1.1 and 2.0:

       <b><a href="postconf.5.html#authorized_verp_clients">authorized_verp_clients</a> ($<a href="postconf.5.html#mynetworks">mynetworks</a>)</b>
              What  remote  SMTP clients are allowed to specify the XVERP com-
              mand.

       Available in Postfix version 2.1 and later:

       <b><a href="postconf.5.html#smtpd_authorized_verp_clients">smtpd_authorized_verp_clients</a> ($<a href="postconf.5.html#authorized_verp_clients">authorized_verp_clients</a>)</b>
              What remote SMTP clients are allowed to specify the  XVERP  com-
              mand.

<b>TROUBLE SHOOTING CONTROLS</b>
       The  <a href="DEBUG_README.html">DEBUG_README</a>  document describes how to debug parts of the Postfix
       mail system. The methods vary from making the software  log  a  lot  of
       detail, to running some daemon processes under control of a call tracer
       or debugger.

       <b><a href="postconf.5.html#debug_peer_level">debug_peer_level</a> (2)</b>
              The increment in verbose logging level when a  nexthop  destina-
              tion,  remote client or server name or network address matches a
              pattern given with the <a href="postconf.5.html#debug_peer_list">debug_peer_list</a> parameter.

       <b><a href="postconf.5.html#debug_peer_list">debug_peer_list</a> (empty)</b>
              Optional list of nexthop destination, remote  client  or  server
              name  or  network  address  patterns that, if matched, cause the
              verbose logging level to increase by  the  amount  specified  in
              $<a href="postconf.5.html#debug_peer_level">debug_peer_level</a>.

       <b><a href="postconf.5.html#error_notice_recipient">error_notice_recipient</a> (postmaster)</b>
              The  recipient  of  postmaster notifications about mail delivery
              problems that are caused by policy, resource, software or proto-
              col errors.

       <b><a href="postconf.5.html#internal_mail_filter_classes">internal_mail_filter_classes</a> (empty)</b>
              What   categories  of  Postfix-generated  mail  are  subject  to
              before-queue   content    inspection    by    <a href="postconf.5.html#non_smtpd_milters">non_smtpd_milters</a>,
              <a href="postconf.5.html#header_checks">header_checks</a> and <a href="postconf.5.html#body_checks">body_checks</a>.

       <b><a href="postconf.5.html#notify_classes">notify_classes</a> (resource, software)</b>
              The list of error classes that are reported to the postmaster.

       <b><a href="postconf.5.html#smtpd_reject_footer">smtpd_reject_footer</a> (empty)</b>
              Optional  information  that  is appended after each Postfix SMTP
              server 4XX or 5XX response.

       <b><a href="postconf.5.html#soft_bounce">soft_bounce</a> (no)</b>
              Safety net to keep mail queued that would otherwise be  returned
              to the sender.

       Available in Postfix version 2.1 and later:

       <b><a href="postconf.5.html#smtpd_authorized_xclient_hosts">smtpd_authorized_xclient_hosts</a> (empty)</b>
              What remote SMTP clients are allowed to use the XCLIENT feature.

       Available in Postfix version 2.10 and later:

       <b><a href="postconf.5.html#smtpd_log_access_permit_actions">smtpd_log_access_permit_actions</a> (empty)</b>
              Enable logging of the named  "permit"  actions  in  SMTP  server
              access  lists (by default, the SMTP server logs "reject" actions
              but not "permit" actions).

<b>KNOWN VERSUS UNKNOWN RECIPIENT CONTROLS</b>
       As of Postfix version 2.0, the SMTP server  rejects  mail  for  unknown
       recipients. This prevents the mail queue from clogging up with undeliv-
       erable MAILER-DAEMON messages. Additional information on this topic  is
       in the <a href="LOCAL_RECIPIENT_README.html">LOCAL_RECIPIENT_README</a> and <a href="ADDRESS_CLASS_README.html">ADDRESS_CLASS_README</a> documents.

       <b><a href="postconf.5.html#show_user_unknown_table_name">show_user_unknown_table_name</a> (yes)</b>
              Display  the  name  of the recipient table in the "User unknown"
              responses.

       <b><a href="postconf.5.html#canonical_maps">canonical_maps</a> (empty)</b>
              Optional address mapping lookup tables for message  headers  and
              envelopes.

       <b><a href="postconf.5.html#recipient_canonical_maps">recipient_canonical_maps</a> (empty)</b>
              Optional  address  mapping lookup tables for envelope and header
              recipient addresses.

       <b><a href="postconf.5.html#sender_canonical_maps">sender_canonical_maps</a> (empty)</b>
              Optional address mapping lookup tables for envelope  and  header
              sender addresses.

       Parameters concerning known/unknown local recipients:

       <b><a href="postconf.5.html#mydestination">mydestination</a> ($<a href="postconf.5.html#myhostname">myhostname</a>, localhost.$<a href="postconf.5.html#mydomain">mydomain</a>, localhost)</b>
              The  list of domains that are delivered via the $<a href="postconf.5.html#local_transport">local_transport</a>
              mail delivery transport.

       <b><a href="postconf.5.html#inet_interfaces">inet_interfaces</a> (all)</b>
              The local network interface  addresses  that  this  mail  system
              receives mail on.

       <b><a href="postconf.5.html#proxy_interfaces">proxy_interfaces</a> (empty)</b>
              The  remote  network  interface  addresses that this mail system
              receives mail on by way of a proxy or network  address  transla-
              tion unit.

       <b><a href="postconf.5.html#inet_protocols">inet_protocols</a> (see 'postconf -d' output)</b>
              The  Internet  protocols Postfix will attempt to use when making
              or accepting connections.

       <b><a href="postconf.5.html#local_recipient_maps">local_recipient_maps</a> (<a href="proxymap.8.html">proxy</a>:unix:passwd.byname $<a href="postconf.5.html#alias_maps">alias_maps</a>)</b>
              Lookup tables with all names or addresses of local recipients: a
              recipient  address  is local when its domain matches $<a href="postconf.5.html#mydestination">mydestina</a>-
              <a href="postconf.5.html#mydestination">tion</a>, $<a href="postconf.5.html#inet_interfaces">inet_interfaces</a> or $<a href="postconf.5.html#proxy_interfaces">proxy_interfaces</a>.

       <b><a href="postconf.5.html#unknown_local_recipient_reject_code">unknown_local_recipient_reject_code</a> (550)</b>
              The numerical Postfix SMTP server response code when a recipient
              address  is local, and $<a href="postconf.5.html#local_recipient_maps">local_recipient_maps</a> specifies a list of
              lookup tables that does not match the recipient.

       Parameters concerning known/unknown recipients of relay destinations:

       <b><a href="postconf.5.html#relay_domains">relay_domains</a> (Postfix</b> &gt;<b>= 3.0: empty, Postfix</b> &lt; <b>3.0: $<a href="postconf.5.html#mydestination">mydestination</a>)</b>
              What destination domains (and subdomains  thereof)  this  system
              will relay mail to.

       <b><a href="postconf.5.html#relay_recipient_maps">relay_recipient_maps</a> (empty)</b>
              Optional  lookup  tables with all valid addresses in the domains
              that match $<a href="postconf.5.html#relay_domains">relay_domains</a>.

       <b><a href="postconf.5.html#unknown_relay_recipient_reject_code">unknown_relay_recipient_reject_code</a> (550)</b>
              The numerical Postfix SMTP server reply code  when  a  recipient
              address  matches $<a href="postconf.5.html#relay_domains">relay_domains</a>, and <a href="postconf.5.html#relay_recipient_maps">relay_recipient_maps</a> speci-
              fies a list of lookup tables that does not match  the  recipient
              address.

       Parameters   concerning   known/unknown  recipients  in  virtual  alias
       domains:

       <b><a href="postconf.5.html#virtual_alias_domains">virtual_alias_domains</a> ($<a href="postconf.5.html#virtual_alias_maps">virtual_alias_maps</a>)</b>
              Postfix is the final destination for the specified list of  vir-
              tual alias domains, that is, domains for which all addresses are
              aliased to addresses in other local or remote domains.

       <b><a href="postconf.5.html#virtual_alias_maps">virtual_alias_maps</a> ($<a href="postconf.5.html#virtual_maps">virtual_maps</a>)</b>
              Optional lookup tables with aliases that apply  to  all  recipi-
              ents:  <a href="local.8.html"><b>local</b>(8)</a>,  virtual, and remote; this is unlike <a href="postconf.5.html#alias_maps">alias_maps</a>
              that apply only to <a href="local.8.html"><b>local</b>(8)</a> recipients.

       <b><a href="postconf.5.html#unknown_virtual_alias_reject_code">unknown_virtual_alias_reject_code</a> (550)</b>
              The Postfix SMTP server reply  code  when  a  recipient  address
              matches  $<a href="postconf.5.html#virtual_alias_domains">virtual_alias_domains</a>,  and $<a href="postconf.5.html#virtual_alias_maps">virtual_alias_maps</a> speci-
              fies a list of lookup tables that does not match  the  recipient
              address.

       Parameters  concerning  known/unknown  recipients  in  virtual  mailbox
       domains:

       <b><a href="postconf.5.html#virtual_mailbox_domains">virtual_mailbox_domains</a> ($<a href="postconf.5.html#virtual_mailbox_maps">virtual_mailbox_maps</a>)</b>
              Postfix is the final  destination  for  the  specified  list  of
              domains;  mail  is  delivered  via  the  $<a href="postconf.5.html#virtual_transport">virtual_transport</a> mail
              delivery transport.

       <b><a href="postconf.5.html#virtual_mailbox_maps">virtual_mailbox_maps</a> (empty)</b>
              Optional lookup tables with all valid addresses in  the  domains
              that match $<a href="postconf.5.html#virtual_mailbox_domains">virtual_mailbox_domains</a>.

       <b><a href="postconf.5.html#unknown_virtual_mailbox_reject_code">unknown_virtual_mailbox_reject_code</a> (550)</b>
              The  Postfix  SMTP  server  reply  code when a recipient address
              matches  $<a href="postconf.5.html#virtual_mailbox_domains">virtual_mailbox_domains</a>,   and   $<a href="postconf.5.html#virtual_mailbox_maps">virtual_mailbox_maps</a>
              specifies a list of lookup tables that does not match the recip-
              ient address.

<b>RESOURCE AND RATE CONTROLS</b>
       The following parameters limit resource usage by the SMTP server and/or
       control client request rates.

       <b><a href="postconf.5.html#line_length_limit">line_length_limit</a> (2048)</b>
              Upon  input,  long  lines  are chopped up into pieces of at most
              this length; upon delivery, long lines are reconstructed.

       <b><a href="postconf.5.html#queue_minfree">queue_minfree</a> (0)</b>
              The minimal amount of free space in bytes in the queue file sys-
              tem that is needed to receive mail.

       <b><a href="postconf.5.html#message_size_limit">message_size_limit</a> (10240000)</b>
              The  maximal  size  in  bytes  of  a message, including envelope
              information.

       <b><a href="postconf.5.html#smtpd_recipient_limit">smtpd_recipient_limit</a> (1000)</b>
              The maximal number of recipients that the  Postfix  SMTP  server
              accepts per message delivery request.

       <b><a href="postconf.5.html#smtpd_timeout">smtpd_timeout</a> (normal: 300s, overload: 10s)</b>
              When  the  Postfix  SMTP  server  wants  to  send an SMTP server
              response, how long the Postfix SMTP  server  will  wait  for  an
              underlying  network  write  operation  to complete; and when the
              Postfix SMTP server Postfix wants  to  receive  an  SMTP  client
              request,  how  long  the  Postfix  SMTP  server will wait for an
              underlying network read operation to complete.

       <b><a href="postconf.5.html#smtpd_history_flush_threshold">smtpd_history_flush_threshold</a> (100)</b>
              The maximal number of lines in the Postfix SMTP  server  command
              history  before it is flushed upon receipt of EHLO, RSET, or end
              of DATA.

       Available in Postfix version 2.3 and later:

       <b><a href="postconf.5.html#smtpd_peername_lookup">smtpd_peername_lookup</a> (yes)</b>
              Attempt to look up the remote SMTP client hostname,  and  verify
              that the name matches the client IP address.

       The per SMTP client connection count and request rate limits are imple-
       mented in co-operation with the <a href="anvil.8.html"><b>anvil</b>(8)</a> service, and are available  in
       Postfix version 2.2 and later.

       <b><a href="postconf.5.html#smtpd_client_connection_count_limit">smtpd_client_connection_count_limit</a> (50)</b>
              How  many simultaneous connections any client is allowed to make
              to this service.

       <b><a href="postconf.5.html#smtpd_client_connection_rate_limit">smtpd_client_connection_rate_limit</a> (0)</b>
              The maximal number of connection attempts any client is  allowed
              to make to this service per time unit.

       <b><a href="postconf.5.html#smtpd_client_message_rate_limit">smtpd_client_message_rate_limit</a> (0)</b>
              The  maximal number of message delivery requests that any client
              is allowed to make to this service per time unit, regardless  of
              whether or not Postfix actually accepts those messages.

       <b><a href="postconf.5.html#smtpd_client_recipient_rate_limit">smtpd_client_recipient_rate_limit</a> (0)</b>
              The  maximal  number  of  recipient addresses that any client is
              allowed to send to this service per  time  unit,  regardless  of
              whether or not Postfix actually accepts those recipients.

       <b><a href="postconf.5.html#smtpd_client_event_limit_exceptions">smtpd_client_event_limit_exceptions</a> ($<a href="postconf.5.html#mynetworks">mynetworks</a>)</b>
              Clients  that  are excluded from smtpd_client_*_count/rate_limit
              restrictions.

       Available in Postfix version 2.3 and later:

       <b><a href="postconf.5.html#smtpd_client_new_tls_session_rate_limit">smtpd_client_new_tls_session_rate_limit</a> (0)</b>
              The maximal number of new (i.e., uncached) TLS sessions  that  a
              remote SMTP client is allowed to negotiate with this service per
              time unit.

       Available in Postfix version 2.9 - 3.6:

       <b><a href="postconf.5.html#smtpd_per_record_deadline">smtpd_per_record_deadline</a> (normal: no, overload: yes)</b>
              Change  the  behavior  of  the  <a href="postconf.5.html#smtpd_timeout">smtpd_timeout</a>  and  <a href="postconf.5.html#smtpd_starttls_timeout">smtpd_start</a>-
              <a href="postconf.5.html#smtpd_starttls_timeout">tls_timeout</a>  time  limits,  from  a time limit per read or write
              system call, to a time limit  to  send  or  receive  a  complete
              record  (an  SMTP command line, SMTP response line, SMTP message
              content line, or TLS protocol message).

       Available in Postfix version 3.1 and later:

       <b><a href="postconf.5.html#smtpd_client_auth_rate_limit">smtpd_client_auth_rate_limit</a> (0)</b>
              The maximal number of AUTH commands that any client  is  allowed
              to  send to this service per time unit, regardless of whether or
              not Postfix actually accepts those commands.

       Available in Postfix version 3.7 and later:

       <b><a href="postconf.5.html#smtpd_per_request_deadline">smtpd_per_request_deadline</a> (normal: no, overload: yes)</b>
              Change  the  behavior  of  the  <a href="postconf.5.html#smtpd_timeout">smtpd_timeout</a>  and  <a href="postconf.5.html#smtpd_starttls_timeout">smtpd_start</a>-
              <a href="postconf.5.html#smtpd_starttls_timeout">tls_timeout</a>  time limits, from a time limit per plaintext or TLS
              read or write call, to a combined time  limit  for  receiving  a
              complete  SMTP request and for sending a complete SMTP response.

       <b><a href="postconf.5.html#smtpd_min_data_rate">smtpd_min_data_rate</a> (500)</b>
              The minimum plaintext data transfer  rate  in  bytes/second  for
              DATA   and  BDAT  requests,  when  deadlines  are  enabled  with
              <a href="postconf.5.html#smtpd_per_request_deadline">smtpd_per_request_deadline</a>.

       <b><a href="postconf.5.html#header_from_format">header_from_format</a> (standard)</b>
              The format of the Postfix-generated <b>From:</b> header.

       Available in Postfix version 3.8 and later:

       <b><a href="postconf.5.html#smtpd_client_ipv4_prefix_length">smtpd_client_ipv4_prefix_length</a> (32)</b>
              Aggregate smtpd_client_*_count and  smtpd_client_*_rate  statis-
              tics by IPv4 network blocks with the specified network prefix.

       <b><a href="postconf.5.html#smtpd_client_ipv6_prefix_length">smtpd_client_ipv6_prefix_length</a> (84)</b>
              Aggregate  smtpd_client_*_count  and smtpd_client_*_rate statis-
              tics by IPv6 network blocks with the specified network prefix.

       Available in Postfix 3.9, 3.8.1, 3.7.6, 3.6.10, 3.5.20 and later:

       <b><a href="postconf.5.html#smtpd_forbid_unauth_pipelining">smtpd_forbid_unauth_pipelining</a> (Postfix</b> &gt;<b>= 3.9: yes)</b>
              Disconnect remote SMTP clients that violate <a href="https://tools.ietf.org/html/rfc2920">RFC 2920</a>  (or  5321)
              command pipelining constraints.

       Available in Postfix 3.9, 3.8.4, 3.7.9, 3.6.13, 3.5.23 and later:

       <b><a href="postconf.5.html#smtpd_forbid_bare_newline">smtpd_forbid_bare_newline</a> (Postfix</b> &gt;<b>= 3.9: normalize)</b>
              Reject  or  restrict input lines from an SMTP client that end in
              &lt;LF&gt; instead of the standard &lt;CR&gt;&lt;LF&gt;.

       <b><a href="postconf.5.html#smtpd_forbid_bare_newline_exclusions">smtpd_forbid_bare_newline_exclusions</a> ($<a href="postconf.5.html#mynetworks">mynetworks</a>)</b>
              Exclude the  specified  clients  from  <a href="postconf.5.html#smtpd_forbid_bare_newline">smtpd_forbid_bare_newline</a>
              enforcement.

       Available in Postfix 3.9, 3.8.5, 3.7.10, 3.6.14, 3.5.24 and later:

       <b><a href="postconf.5.html#smtpd_forbid_bare_newline_reject_code">smtpd_forbid_bare_newline_reject_code</a> (550)</b>
              The numerical Postfix SMTP server response code when rejecting a
              request with "<a href="postconf.5.html#smtpd_forbid_bare_newline">smtpd_forbid_bare_newline</a> = reject".

<b>TARPIT CONTROLS</b>
       When a remote SMTP client makes errors, the  Postfix  SMTP  server  can
       insert  delays  before  responding. This can help to slow down run-away
       software.  The behavior is controlled by an error counter  that  counts
       the number of errors within an SMTP session that a client makes without
       delivering mail.

       <b><a href="postconf.5.html#smtpd_error_sleep_time">smtpd_error_sleep_time</a> (1s)</b>
              With Postfix version 2.1 and later:  the  SMTP  server  response
              delay  after a client has made more than $<a href="postconf.5.html#smtpd_soft_error_limit">smtpd_soft_error_limit</a>
              errors, and fewer than $<a href="postconf.5.html#smtpd_hard_error_limit">smtpd_hard_error_limit</a>  errors,  without
              delivering mail.

       <b><a href="postconf.5.html#smtpd_soft_error_limit">smtpd_soft_error_limit</a> (10)</b>
              The  number  of  errors  a remote SMTP client is allowed to make
              without delivering mail before the  Postfix  SMTP  server  slows
              down all its responses.

       <b><a href="postconf.5.html#smtpd_hard_error_limit">smtpd_hard_error_limit</a> (normal: 20, overload: 1)</b>
              The  maximal number of errors a remote SMTP client is allowed to
              make without delivering mail.

       <b><a href="postconf.5.html#smtpd_junk_command_limit">smtpd_junk_command_limit</a> (normal: 100, overload: 1)</b>
              The number of junk commands (NOOP, VRFY, ETRN or  RSET)  that  a
              remote  SMTP  client  can  send  before  the Postfix SMTP server
              starts to increment the error counter with each junk command.

       Available in Postfix version 2.1 and later:

       <b><a href="postconf.5.html#smtpd_recipient_overshoot_limit">smtpd_recipient_overshoot_limit</a> (1000)</b>
              The number of recipients that a remote SMTP client can  send  in
              excess  of  the  limit  specified  with  $<a href="postconf.5.html#smtpd_recipient_limit">smtpd_recipient_limit</a>,
              before the Postfix SMTP server increments the per-session  error
              count for each excess recipient.

<b>ACCESS POLICY DELEGATION CONTROLS</b>
       As  of version 2.1, Postfix can be configured to delegate access policy
       decisions to an external server that runs  outside  Postfix.   See  the
       file <a href="SMTPD_POLICY_README.html">SMTPD_POLICY_README</a> for more information.

       <b><a href="postconf.5.html#smtpd_policy_service_max_idle">smtpd_policy_service_max_idle</a> (300s)</b>
              The  time after which an idle SMTPD policy service connection is
              closed.

       <b><a href="postconf.5.html#smtpd_policy_service_max_ttl">smtpd_policy_service_max_ttl</a> (1000s)</b>
              The time after which an active SMTPD policy  service  connection
              is closed.

       <b><a href="postconf.5.html#smtpd_policy_service_timeout">smtpd_policy_service_timeout</a> (100s)</b>
              The  time limit for connecting to, writing to, or receiving from
              a delegated SMTPD policy server.

       Available in Postfix version 3.0 and later:

       <b><a href="postconf.5.html#smtpd_policy_service_default_action">smtpd_policy_service_default_action</a>  (451  4.3.5  Server  configuration</b>
       <b>problem)</b>
              The default action when an SMTPD policy service request fails.

       <b><a href="postconf.5.html#smtpd_policy_service_request_limit">smtpd_policy_service_request_limit</a> (0)</b>
              The maximal number of requests per SMTPD policy service  connec-
              tion, or zero (no limit).

       <b><a href="postconf.5.html#smtpd_policy_service_try_limit">smtpd_policy_service_try_limit</a> (2)</b>
              The  maximal  number of attempts to send an SMTPD policy service
              request before giving up.

       <b><a href="postconf.5.html#smtpd_policy_service_retry_delay">smtpd_policy_service_retry_delay</a> (1s)</b>
              The delay between attempts to resend a failed SMTPD policy  ser-
              vice request.

       Available in Postfix version 3.1 and later:

       <b><a href="postconf.5.html#smtpd_policy_service_policy_context">smtpd_policy_service_policy_context</a> (empty)</b>
              Optional  information  that the Postfix SMTP server specifies in
              the "policy_context"  attribute  of  a  policy  service  request
              (originally,  to  share the same service endpoint among multiple
              <a href="postconf.5.html#check_policy_service">check_policy_service</a> clients).

<b>ACCESS CONTROLS</b>
       The <a href="SMTPD_ACCESS_README.html">SMTPD_ACCESS_README</a> document gives an introduction to all the  SMTP
       server access control features.

       <b><a href="postconf.5.html#smtpd_delay_reject">smtpd_delay_reject</a> (yes)</b>
              Wait    until    the   RCPT   TO   command   before   evaluating
              $<a href="postconf.5.html#smtpd_client_restrictions">smtpd_client_restrictions</a>,     $<a href="postconf.5.html#smtpd_helo_restrictions">smtpd_helo_restrictions</a>     and
              $<a href="postconf.5.html#smtpd_sender_restrictions">smtpd_sender_restrictions</a>,  or  wait  until  the  ETRN  command
              before      evaluating      $<a href="postconf.5.html#smtpd_client_restrictions">smtpd_client_restrictions</a>       and
              $<a href="postconf.5.html#smtpd_helo_restrictions">smtpd_helo_restrictions</a>.

       <b><a href="postconf.5.html#parent_domain_matches_subdomains">parent_domain_matches_subdomains</a> (see 'postconf -d' output)</b>
              A  list of Postfix features where the pattern "example.com" also
              matches subdomains  of  example.com,  instead  of  requiring  an
              explicit ".example.com" pattern.

       <b><a href="postconf.5.html#smtpd_client_restrictions">smtpd_client_restrictions</a> (empty)</b>
              Optional  restrictions  that  the Postfix SMTP server applies in
              the context of a client connection request.

       <b><a href="postconf.5.html#smtpd_helo_required">smtpd_helo_required</a> (no)</b>
              Require that a remote SMTP client  introduces  itself  with  the
              HELO  or  EHLO  command before sending the MAIL command or other
              commands that require EHLO negotiation.

       <b><a href="postconf.5.html#smtpd_helo_restrictions">smtpd_helo_restrictions</a> (empty)</b>
              Optional restrictions that the Postfix SMTP  server  applies  in
              the context of a client HELO command.

       <b><a href="postconf.5.html#smtpd_sender_restrictions">smtpd_sender_restrictions</a> (empty)</b>
              Optional  restrictions  that  the Postfix SMTP server applies in
              the context of a client MAIL FROM command.

       <b><a href="postconf.5.html#smtpd_recipient_restrictions">smtpd_recipient_restrictions</a> (see 'postconf -d' output)</b>
              Optional restrictions that the Postfix SMTP  server  applies  in
              the    context    of   a   client   RCPT   TO   command,   after
              <a href="postconf.5.html#smtpd_relay_restrictions">smtpd_relay_restrictions</a>.

       <b><a href="postconf.5.html#smtpd_etrn_restrictions">smtpd_etrn_restrictions</a> (empty)</b>
              Optional restrictions that the Postfix SMTP  server  applies  in
              the context of a client ETRN command.

       <b><a href="postconf.5.html#allow_untrusted_routing">allow_untrusted_routing</a> (no)</b>
              Forward       mail       with      sender-specified      routing
              (user[@%!]remote[@%!]site) from untrusted  clients  to  destina-
              tions matching $<a href="postconf.5.html#relay_domains">relay_domains</a>.

       <b><a href="postconf.5.html#smtpd_restriction_classes">smtpd_restriction_classes</a> (empty)</b>
              User-defined aliases for groups of access restrictions.

       <b><a href="postconf.5.html#smtpd_null_access_lookup_key">smtpd_null_access_lookup_key</a> (</b>&lt;&gt;<b>)</b>
              The  lookup  key  to be used in SMTP <a href="access.5.html"><b>access</b>(5)</a> tables instead of
              the null sender address.

       <b><a href="postconf.5.html#permit_mx_backup_networks">permit_mx_backup_networks</a> (empty)</b>
              Restrict the use of the <a href="postconf.5.html#permit_mx_backup">permit_mx_backup</a> SMTP access feature  to
              only domains whose primary MX hosts match the listed networks.

       Available in Postfix version 2.0 and later:

       <b><a href="postconf.5.html#smtpd_data_restrictions">smtpd_data_restrictions</a> (empty)</b>
              Optional  access  restrictions  that  the  Postfix  SMTP  server
              applies in the context of the SMTP DATA command.

       <b><a href="postconf.5.html#smtpd_expansion_filter">smtpd_expansion_filter</a> (see 'postconf -d' output)</b>
              What characters are allowed in $name  expansions  of  RBL  reply
              templates.

       Available in Postfix version 2.1 and later:

       <b><a href="postconf.5.html#smtpd_reject_unlisted_sender">smtpd_reject_unlisted_sender</a> (no)</b>
              Request  that  the Postfix SMTP server rejects mail from unknown
              sender addresses, even when no  explicit  <a href="postconf.5.html#reject_unlisted_sender">reject_unlisted_sender</a>
              access restriction is specified.

       <b><a href="postconf.5.html#smtpd_reject_unlisted_recipient">smtpd_reject_unlisted_recipient</a> (yes)</b>
              Request  that  the  Postfix SMTP server rejects mail for unknown
              recipient     addresses,     even     when      no      explicit
              <a href="postconf.5.html#reject_unlisted_recipient">reject_unlisted_recipient</a> access restriction is specified.

       Available in Postfix version 2.2 and later:

       <b><a href="postconf.5.html#smtpd_end_of_data_restrictions">smtpd_end_of_data_restrictions</a> (empty)</b>
              Optional  access  restrictions  that  the  Postfix  SMTP  server
              applies in the context of the SMTP END-OF-DATA command.

       Available in Postfix version 2.10 and later:

       <b><a href="postconf.5.html#smtpd_relay_restrictions">smtpd_relay_restrictions</a> (<a href="postconf.5.html#permit_mynetworks">permit_mynetworks</a>, <a href="postconf.5.html#permit_sasl_authenticated">permit_sasl_authenticated</a>,</b>
       <b><a href="postconf.5.html#defer_unauth_destination">defer_unauth_destination</a>)</b>
              Access restrictions for mail relay control that the Postfix SMTP
              server  applies  in  the  context of the RCPT TO command, before
              <a href="postconf.5.html#smtpd_recipient_restrictions">smtpd_recipient_restrictions</a>.

<b>SENDER AND RECIPIENT ADDRESS VERIFICATION CONTROLS</b>
       Postfix version 2.1 introduces sender and recipient  address  verifica-
       tion.  This feature is implemented by sending probe email messages that
       are  not  actually  delivered.   This  feature  is  requested  via  the
       <a href="postconf.5.html#reject_unverified_sender">reject_unverified_sender</a>    and    <a href="postconf.5.html#reject_unverified_recipient">reject_unverified_recipient</a>   access
       restrictions.  The status of verification probes is maintained  by  the
       <a href="verify.8.html"><b>verify</b>(8)</a>  server.  See the file <a href="ADDRESS_VERIFICATION_README.html">ADDRESS_VERIFICATION_README</a> for infor-
       mation about how to configure and operate the Postfix  sender/recipient
       address verification service.

       <b><a href="postconf.5.html#address_verify_poll_count">address_verify_poll_count</a> (normal: 3, overload: 1)</b>
              How many times to query the <a href="verify.8.html"><b>verify</b>(8)</a> service for the completion
              of an address verification request in progress.

       <b><a href="postconf.5.html#address_verify_poll_delay">address_verify_poll_delay</a> (3s)</b>
              The delay between queries for the completion of an address veri-
              fication request in progress.

       <b><a href="postconf.5.html#address_verify_sender">address_verify_sender</a> ($<a href="postconf.5.html#double_bounce_sender">double_bounce_sender</a>)</b>
              The  sender address to use in address verification probes; prior
              to Postfix 2.5 the default was "postmaster".

       <b><a href="postconf.5.html#unverified_sender_reject_code">unverified_sender_reject_code</a> (450)</b>
              The numerical Postfix SMTP server response code when a recipient
              address is rejected by the <a href="postconf.5.html#reject_unverified_sender">reject_unverified_sender</a> restriction.

       <b><a href="postconf.5.html#unverified_recipient_reject_code">unverified_recipient_reject_code</a> (450)</b>
              The numerical Postfix SMTP  server  response  when  a  recipient
              address  is rejected by the <a href="postconf.5.html#reject_unverified_recipient">reject_unverified_recipient</a> restric-
              tion.

       Available in Postfix version 2.6 and later:

       <b><a href="postconf.5.html#unverified_sender_defer_code">unverified_sender_defer_code</a> (450)</b>
              The numerical Postfix SMTP server response code  when  a  sender
              address probe fails due to a temporary error condition.

       <b><a href="postconf.5.html#unverified_recipient_defer_code">unverified_recipient_defer_code</a> (450)</b>
              The  numerical  Postfix  SMTP  server  response when a recipient
              address probe fails due to a temporary error condition.

       <b><a href="postconf.5.html#unverified_sender_reject_reason">unverified_sender_reject_reason</a> (empty)</b>
              The  Postfix  SMTP  server's  reply  when  rejecting  mail  with
              <a href="postconf.5.html#reject_unverified_sender">reject_unverified_sender</a>.

       <b><a href="postconf.5.html#unverified_recipient_reject_reason">unverified_recipient_reject_reason</a> (empty)</b>
              The  Postfix  SMTP  server's  reply  when  rejecting  mail  with
              <a href="postconf.5.html#reject_unverified_recipient">reject_unverified_recipient</a>.

       <b><a href="postconf.5.html#unverified_sender_tempfail_action">unverified_sender_tempfail_action</a> ($<a href="postconf.5.html#reject_tempfail_action">reject_tempfail_action</a>)</b>
              The Postfix SMTP server's action  when  <a href="postconf.5.html#reject_unverified_sender">reject_unverified_sender</a>
              fails due to a temporary error condition.

       <b><a href="postconf.5.html#unverified_recipient_tempfail_action">unverified_recipient_tempfail_action</a> ($<a href="postconf.5.html#reject_tempfail_action">reject_tempfail_action</a>)</b>
              The  Postfix SMTP server's action when <a href="postconf.5.html#reject_unverified_recipient">reject_unverified_recipi</a>-
              <a href="postconf.5.html#reject_unverified_recipient">ent</a> fails due to a temporary error condition.

       Available with Postfix 2.9 and later:

       <b><a href="postconf.5.html#address_verify_sender_ttl">address_verify_sender_ttl</a> (0s)</b>
              The time  between  changes  in  the  time-dependent  portion  of
              address verification probe sender addresses.

<b>ACCESS CONTROL RESPONSES</b>
       The following parameters control numerical SMTP reply codes and/or text
       responses.

       <b><a href="postconf.5.html#access_map_reject_code">access_map_reject_code</a> (554)</b>
              The numerical Postfix SMTP server response code for an <a href="access.5.html"><b>access</b>(5)</a>
              map "reject" action.

       <b><a href="postconf.5.html#defer_code">defer_code</a> (450)</b>
              The  numerical  Postfix  SMTP server response code when a remote
              SMTP client request is rejected by the "defer" restriction.

       <b><a href="postconf.5.html#invalid_hostname_reject_code">invalid_hostname_reject_code</a> (501)</b>
              The numerical Postfix SMTP server response code when the  client
              HELO   or   EHLO   command   parameter   is   rejected   by  the
              <a href="postconf.5.html#reject_invalid_helo_hostname">reject_invalid_helo_hostname</a> restriction.

       <b><a href="postconf.5.html#maps_rbl_reject_code">maps_rbl_reject_code</a> (554)</b>
              The numerical Postfix SMTP server response code  when  a  remote
              SMTP   client  request  is  blocked  by  the  <a href="postconf.5.html#reject_rbl_client">reject_rbl_client</a>,
              <a href="postconf.5.html#reject_rhsbl_client">reject_rhsbl_client</a>,                <a href="postconf.5.html#reject_rhsbl_reverse_client">reject_rhsbl_reverse_client</a>,
              <a href="postconf.5.html#reject_rhsbl_sender">reject_rhsbl_sender</a> or <a href="postconf.5.html#reject_rhsbl_recipient">reject_rhsbl_recipient</a> restriction.

       <b><a href="postconf.5.html#non_fqdn_reject_code">non_fqdn_reject_code</a> (504)</b>
              The  numerical  Postfix  SMTP  server  reply  code when a client
              request  is  rejected  by   the   <a href="postconf.5.html#reject_non_fqdn_helo_hostname">reject_non_fqdn_helo_hostname</a>,
              <a href="postconf.5.html#reject_non_fqdn_sender">reject_non_fqdn_sender</a> or <a href="postconf.5.html#reject_non_fqdn_recipient">reject_non_fqdn_recipient</a> restriction.

       <b><a href="postconf.5.html#plaintext_reject_code">plaintext_reject_code</a> (450)</b>
              The numerical Postfix SMTP server response code when  a  request
              is rejected by the <b><a href="postconf.5.html#reject_plaintext_session">reject_plaintext_session</a></b> restriction.

       <b><a href="postconf.5.html#reject_code">reject_code</a> (554)</b>
              The  numerical  Postfix  SMTP server response code when a remote
              SMTP client request is rejected by the "reject" restriction.

       <b><a href="postconf.5.html#relay_domains_reject_code">relay_domains_reject_code</a> (554)</b>
              The numerical Postfix SMTP server response code  when  a  client
              request  is  rejected by the <a href="postconf.5.html#reject_unauth_destination">reject_unauth_destination</a> recipient
              restriction.

       <b><a href="postconf.5.html#unknown_address_reject_code">unknown_address_reject_code</a> (450)</b>
              The numerical response code when the Postfix SMTP server rejects
              a sender or recipient address because its domain is unknown.

       <b><a href="postconf.5.html#unknown_client_reject_code">unknown_client_reject_code</a> (450)</b>
              The  numerical  Postfix  SMTP server response code when a client
              without valid address  &lt;=&gt;  name  mapping  is  rejected  by  the
              <a href="postconf.5.html#reject_unknown_client_hostname">reject_unknown_client_hostname</a> restriction.

       <b><a href="postconf.5.html#unknown_hostname_reject_code">unknown_hostname_reject_code</a> (450)</b>
              The  numerical  Postfix SMTP server response code when the host-
              name specified with the HELO or EHLO command is rejected by  the
              <a href="postconf.5.html#reject_unknown_helo_hostname">reject_unknown_helo_hostname</a> restriction.

       Available in Postfix version 2.0 and later:

       <b><a href="postconf.5.html#default_rbl_reply">default_rbl_reply</a> (see 'postconf -d' output)</b>
              The  default Postfix SMTP server response template for a request
              that is rejected by an RBL-based restriction.

       <b><a href="postconf.5.html#multi_recipient_bounce_reject_code">multi_recipient_bounce_reject_code</a> (550)</b>
              The numerical Postfix SMTP server response code  when  a  remote
              SMTP  client  request  is  blocked  by  the <a href="postconf.5.html#reject_multi_recipient_bounce">reject_multi_recipi</a>-
              <a href="postconf.5.html#reject_multi_recipient_bounce">ent_bounce</a> restriction.

       <b><a href="postconf.5.html#rbl_reply_maps">rbl_reply_maps</a> (empty)</b>
              Optional lookup tables with RBL response templates.

       Available in Postfix version 2.6 and later:

       <b><a href="postconf.5.html#access_map_defer_code">access_map_defer_code</a> (450)</b>
              The numerical Postfix SMTP server response code for an <a href="access.5.html"><b>access</b>(5)</a>
              map    "defer"    action,    including    "<a href="postconf.5.html#defer_if_permit">defer_if_permit</a>"   or
              "<a href="postconf.5.html#defer_if_reject">defer_if_reject</a>".

       <b><a href="postconf.5.html#reject_tempfail_action">reject_tempfail_action</a> (<a href="postconf.5.html#defer_if_permit">defer_if_permit</a>)</b>
              The Postfix SMTP server's action when a reject-type  restriction
              fails due to a temporary error condition.

       <b><a href="postconf.5.html#unknown_helo_hostname_tempfail_action">unknown_helo_hostname_tempfail_action</a> ($<a href="postconf.5.html#reject_tempfail_action">reject_tempfail_action</a>)</b>
              The  Postfix SMTP server's action when <a href="postconf.5.html#reject_unknown_helo_hostname">reject_unknown_helo_host</a>-
              <a href="postconf.5.html#reject_unknown_helo_hostname">name</a> fails due to a temporary error condition.

       <b><a href="postconf.5.html#unknown_address_tempfail_action">unknown_address_tempfail_action</a> ($<a href="postconf.5.html#reject_tempfail_action">reject_tempfail_action</a>)</b>
              The      Postfix      SMTP      server's       action       when
              <a href="postconf.5.html#reject_unknown_sender_domain">reject_unknown_sender_domain</a>  or <a href="postconf.5.html#reject_unknown_recipient_domain">reject_unknown_recipient_domain</a>
              fail due to a temporary error condition.

<b>MISCELLANEOUS CONTROLS</b>
       <b><a href="postconf.5.html#config_directory">config_directory</a> (see 'postconf -d' output)</b>
              The default location of the Postfix <a href="postconf.5.html">main.cf</a> and  <a href="master.5.html">master.cf</a>  con-
              figuration files.

       <b><a href="postconf.5.html#daemon_timeout">daemon_timeout</a> (18000s)</b>
              How  much  time  a  Postfix  daemon process may take to handle a
              request before it is terminated by a built-in watchdog timer.

       <b><a href="postconf.5.html#command_directory">command_directory</a> (see 'postconf -d' output)</b>
              The location of all postfix administrative commands.

       <b><a href="postconf.5.html#double_bounce_sender">double_bounce_sender</a> (double-bounce)</b>
              The sender address of postmaster notifications that  are  gener-
              ated by the mail system.

       <b><a href="postconf.5.html#ipc_timeout">ipc_timeout</a> (3600s)</b>
              The  time  limit  for  sending  or receiving information over an
              internal communication channel.

       <b><a href="postconf.5.html#mail_name">mail_name</a> (Postfix)</b>
              The mail system name that is displayed in Received: headers,  in
              the SMTP greeting banner, and in bounced mail.

       <b><a href="postconf.5.html#mail_owner">mail_owner</a> (postfix)</b>
              The  UNIX  system  account  that owns the Postfix queue and most
              Postfix daemon processes.

       <b><a href="postconf.5.html#max_idle">max_idle</a> (100s)</b>
              The maximum amount of time that an idle Postfix  daemon  process
              waits for an incoming connection before terminating voluntarily.

       <b><a href="postconf.5.html#max_use">max_use</a> (100)</b>
              The maximal number of incoming connections that a Postfix daemon
              process will service before terminating voluntarily.

       <b><a href="postconf.5.html#myhostname">myhostname</a> (see 'postconf -d' output)</b>
              The internet hostname of this mail system.

       <b><a href="postconf.5.html#mynetworks">mynetworks</a> (see 'postconf -d' output)</b>
              The  list of "trusted" remote SMTP clients that have more privi-
              leges than "strangers".

       <b><a href="postconf.5.html#myorigin">myorigin</a> ($<a href="postconf.5.html#myhostname">myhostname</a>)</b>
              The domain name that locally-posted mail appears to  come  from,
              and that locally posted mail is delivered to.

       <b><a href="postconf.5.html#process_id">process_id</a> (read-only)</b>
              The process ID of a Postfix command or daemon process.

       <b><a href="postconf.5.html#process_name">process_name</a> (read-only)</b>
              The process name of a Postfix command or daemon process.

       <b><a href="postconf.5.html#queue_directory">queue_directory</a> (see 'postconf -d' output)</b>
              The location of the Postfix top-level queue directory.

       <b><a href="postconf.5.html#recipient_delimiter">recipient_delimiter</a> (empty)</b>
              The  set of characters that can separate an email address local-
              part, user name, or a .forward file name from its extension.

       <b><a href="postconf.5.html#smtpd_banner">smtpd_banner</a> ($<a href="postconf.5.html#myhostname">myhostname</a> ESMTP $<a href="postconf.5.html#mail_name">mail_name</a>)</b>
              The text that follows the 220 status code in the  SMTP  greeting
              banner.

       <b><a href="postconf.5.html#syslog_facility">syslog_facility</a> (mail)</b>
              The syslog facility of Postfix logging.

       <b><a href="postconf.5.html#syslog_name">syslog_name</a> (see 'postconf -d' output)</b>
              A  prefix  that  is  prepended  to  the  process  name in syslog
              records, so that, for example, "smtpd" becomes "prefix/smtpd".

       Available in Postfix version 2.2 and later:

       <b><a href="postconf.5.html#smtpd_forbidden_commands">smtpd_forbidden_commands</a> (CONNECT GET POST <a href="regexp_table.5.html">regexp</a>:{{/^[^A-Z]/ Bogus}})</b>
              List of commands that cause the Postfix SMTP server  to  immedi-
              ately terminate the session with a 221 code.

       Available in Postfix version 2.5 and later:

       <b><a href="postconf.5.html#smtpd_client_port_logging">smtpd_client_port_logging</a> (no)</b>
              Enable logging of the remote SMTP client port in addition to the
              hostname and IP address.

       Available in Postfix 3.3 and later:

       <b><a href="postconf.5.html#service_name">service_name</a> (read-only)</b>
              The <a href="master.5.html">master.cf</a> service name of a Postfix daemon process.

       Available in Postfix 3.4 and later:

       <b><a href="postconf.5.html#smtpd_reject_footer_maps">smtpd_reject_footer_maps</a> (empty)</b>
              Lookup tables, indexed by the complete Postfix SMTP  server  4xx
              or 5xx response, with reject footer templates.

<b>SEE ALSO</b>
       <a href="anvil.8.html">anvil(8)</a>, connection/rate limiting
       <a href="cleanup.8.html">cleanup(8)</a>, message canonicalization
       <a href="tlsmgr.8.html">tlsmgr(8)</a>, TLS session and PRNG management
       <a href="trivial-rewrite.8.html">trivial-rewrite(8)</a>, address resolver
       <a href="verify.8.html">verify(8)</a>, address verification service
       <a href="postconf.5.html">postconf(5)</a>, configuration parameters
       <a href="master.5.html">master(5)</a>, generic daemon options
       <a href="master.8.html">master(8)</a>, process manager
       <a href="postlogd.8.html">postlogd(8)</a>, Postfix logging
       syslogd(8), system logging

<b>README FILES</b>
       <a href="ADDRESS_CLASS_README.html">ADDRESS_CLASS_README</a>, blocking unknown hosted or relay recipients
       <a href="ADDRESS_REWRITING_README.html">ADDRESS_REWRITING_README</a>, Postfix address manipulation
       <a href="BDAT_README.html">BDAT_README</a>, Postfix CHUNKING support
       <a href="FILTER_README.html">FILTER_README</a>, external after-queue content filter
       <a href="LOCAL_RECIPIENT_README.html">LOCAL_RECIPIENT_README</a>, blocking unknown local recipients
       <a href="MILTER_README.html">MILTER_README</a>, before-queue mail filter applications
       <a href="SMTPD_ACCESS_README.html">SMTPD_ACCESS_README</a>, built-in access policies
       <a href="SMTPD_POLICY_README.html">SMTPD_POLICY_README</a>, external policy server
       <a href="SMTPD_PROXY_README.html">SMTPD_PROXY_README</a>, external before-queue content filter
       <a href="SASL_README.html">SASL_README</a>, Postfix SASL howto
       <a href="TLS_README.html">TLS_README</a>, Postfix STARTTLS howto
       <a href="VERP_README.html">VERP_README</a>, Postfix XVERP extension
       <a href="XCLIENT_README.html">XCLIENT_README</a>, Postfix XCLIENT extension
       <a href="XFORWARD_README.html">XFORWARD_README</a>, Postfix XFORWARD extension

<b>LICENSE</b>
       The Secure Mailer license must be distributed with this software.

<b>AUTHOR(S)</b>
       Wietse Venema
       IBM T.J. Watson Research
       P.O. Box 704
       Yorktown Heights, NY 10598, USA

       Wietse Venema
       Google, Inc.
       111 8th Avenue
       New York, NY 10011, USA

       SASL support originally by:
       Till Franke
       SuSE Rhein/Main AG
       65760 Eschborn, Germany

       TLS support originally by:
       Lutz Jaenicke
       BTU Cottbus
       Allgemeine Elektrotechnik
       Universitaetsplatz 3-4
       D-03044 Cottbus, Germany

       Revised TLS support by:
       Victor Duchovni
       Morgan Stanley

                                                                      SMTPD(8)
</pre> </body> </html>