File: rfc1894.txt

package info (click to toggle)
doc-rfc 20181229-2
  • links: PTS, VCS
  • area: non-free
  • in suites: buster
  • size: 570,944 kB
  • sloc: xml: 285,646; sh: 107; python: 90; perl: 42; makefile: 14
file content (2187 lines) | stat: -rw-r--r-- 77,462 bytes parent folder | download | duplicates (11)
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
1492
1493
1494
1495
1496
1497
1498
1499
1500
1501
1502
1503
1504
1505
1506
1507
1508
1509
1510
1511
1512
1513
1514
1515
1516
1517
1518
1519
1520
1521
1522
1523
1524
1525
1526
1527
1528
1529
1530
1531
1532
1533
1534
1535
1536
1537
1538
1539
1540
1541
1542
1543
1544
1545
1546
1547
1548
1549
1550
1551
1552
1553
1554
1555
1556
1557
1558
1559
1560
1561
1562
1563
1564
1565
1566
1567
1568
1569
1570
1571
1572
1573
1574
1575
1576
1577
1578
1579
1580
1581
1582
1583
1584
1585
1586
1587
1588
1589
1590
1591
1592
1593
1594
1595
1596
1597
1598
1599
1600
1601
1602
1603
1604
1605
1606
1607
1608
1609
1610
1611
1612
1613
1614
1615
1616
1617
1618
1619
1620
1621
1622
1623
1624
1625
1626
1627
1628
1629
1630
1631
1632
1633
1634
1635
1636
1637
1638
1639
1640
1641
1642
1643
1644
1645
1646
1647
1648
1649
1650
1651
1652
1653
1654
1655
1656
1657
1658
1659
1660
1661
1662
1663
1664
1665
1666
1667
1668
1669
1670
1671
1672
1673
1674
1675
1676
1677
1678
1679
1680
1681
1682
1683
1684
1685
1686
1687
1688
1689
1690
1691
1692
1693
1694
1695
1696
1697
1698
1699
1700
1701
1702
1703
1704
1705
1706
1707
1708
1709
1710
1711
1712
1713
1714
1715
1716
1717
1718
1719
1720
1721
1722
1723
1724
1725
1726
1727
1728
1729
1730
1731
1732
1733
1734
1735
1736
1737
1738
1739
1740
1741
1742
1743
1744
1745
1746
1747
1748
1749
1750
1751
1752
1753
1754
1755
1756
1757
1758
1759
1760
1761
1762
1763
1764
1765
1766
1767
1768
1769
1770
1771
1772
1773
1774
1775
1776
1777
1778
1779
1780
1781
1782
1783
1784
1785
1786
1787
1788
1789
1790
1791
1792
1793
1794
1795
1796
1797
1798
1799
1800
1801
1802
1803
1804
1805
1806
1807
1808
1809
1810
1811
1812
1813
1814
1815
1816
1817
1818
1819
1820
1821
1822
1823
1824
1825
1826
1827
1828
1829
1830
1831
1832
1833
1834
1835
1836
1837
1838
1839
1840
1841
1842
1843
1844
1845
1846
1847
1848
1849
1850
1851
1852
1853
1854
1855
1856
1857
1858
1859
1860
1861
1862
1863
1864
1865
1866
1867
1868
1869
1870
1871
1872
1873
1874
1875
1876
1877
1878
1879
1880
1881
1882
1883
1884
1885
1886
1887
1888
1889
1890
1891
1892
1893
1894
1895
1896
1897
1898
1899
1900
1901
1902
1903
1904
1905
1906
1907
1908
1909
1910
1911
1912
1913
1914
1915
1916
1917
1918
1919
1920
1921
1922
1923
1924
1925
1926
1927
1928
1929
1930
1931
1932
1933
1934
1935
1936
1937
1938
1939
1940
1941
1942
1943
1944
1945
1946
1947
1948
1949
1950
1951
1952
1953
1954
1955
1956
1957
1958
1959
1960
1961
1962
1963
1964
1965
1966
1967
1968
1969
1970
1971
1972
1973
1974
1975
1976
1977
1978
1979
1980
1981
1982
1983
1984
1985
1986
1987
1988
1989
1990
1991
1992
1993
1994
1995
1996
1997
1998
1999
2000
2001
2002
2003
2004
2005
2006
2007
2008
2009
2010
2011
2012
2013
2014
2015
2016
2017
2018
2019
2020
2021
2022
2023
2024
2025
2026
2027
2028
2029
2030
2031
2032
2033
2034
2035
2036
2037
2038
2039
2040
2041
2042
2043
2044
2045
2046
2047
2048
2049
2050
2051
2052
2053
2054
2055
2056
2057
2058
2059
2060
2061
2062
2063
2064
2065
2066
2067
2068
2069
2070
2071
2072
2073
2074
2075
2076
2077
2078
2079
2080
2081
2082
2083
2084
2085
2086
2087
2088
2089
2090
2091
2092
2093
2094
2095
2096
2097
2098
2099
2100
2101
2102
2103
2104
2105
2106
2107
2108
2109
2110
2111
2112
2113
2114
2115
2116
2117
2118
2119
2120
2121
2122
2123
2124
2125
2126
2127
2128
2129
2130
2131
2132
2133
2134
2135
2136
2137
2138
2139
2140
2141
2142
2143
2144
2145
2146
2147
2148
2149
2150
2151
2152
2153
2154
2155
2156
2157
2158
2159
2160
2161
2162
2163
2164
2165
2166
2167
2168
2169
2170
2171
2172
2173
2174
2175
2176
2177
2178
2179
2180
2181
2182
2183
2184
2185
2186
2187






Network Working Group                                           K. Moore
Request for Comments: 1894                       University of Tennessee
Category: Standards Track                                   G. Vaudreuil
                                                  Octel Network Services
                                                            January 1996


     An Extensible Message Format for Delivery Status Notifications

Status of this Memo

   This document specifies an Internet standards track protocol for the
   Internet community, and requests discussion and suggestions for
   improvements.  Please refer to the current edition of the "Internet
   Official Protocol Standards" (STD 1) for the standardization state
   and status of this protocol.  Distribution of this memo is unlimited.

Abstract

   This memo defines a MIME content-type that may be used by a message
   transfer agent (MTA) or electronic mail gateway to report the result
   of an attempt to deliver a message to one or more recipients.  This
   content-type is intended as a machine-processable replacement for the
   various types of delivery status notifications currently used in
   Internet electronic mail.

   Because many messages are sent between the Internet and other
   messaging systems (such as X.400 or the so-called "LAN-based"
   systems), the DSN protocol is designed to be useful in a multi-
   protocol messaging environment.  To this end, the protocol described
   in this memo provides for the carriage of "foreign" addresses and
   error codes, in addition to those normally used in Internet mail.
   Additional attributes may also be defined to support "tunneling" of
   foreign notifications through Internet mail.

   Any questions, comments, and reports of defects or ambiguities in
   this specification may be sent to the mailing list for the NOTARY
   working group of the IETF, using the address
   <notifications@cs.utk.edu>.  Requests to subscribe to the mailing
   list should be addressed to <notifications-request@cs.utk.edu>.
   Implementors of this specification are encouraged to subscribe to the
   mailing list, so that they will quickly be informed of any problems
   which might hinder interoperability.

   NOTE: This document is a Proposed Standard.  If and when this
   protocol is submitted for Draft Standard status, any normative text
   (phrases containing SHOULD, SHOULD NOT, MUST, MUST NOT, or MAY) in
   this document will be re-evaluated in light of implementation



Moore & Vaudreuil           Standards Track                     [Page 1]

RFC 1894             Delivery Status Notifications          January 1996


   experience, and are thus subject to change.

1. Introduction

   This memo defines a MIME [1] content-type for delivery status
   notifications (DSNs).  A DSN can be used to notify the sender of a
   message of any of several conditions:  failed delivery, delayed
   delivery, successful delivery, or the gatewaying of a message into an
   environment that may not support DSNs.  The "message/delivery-status"
   content-type defined herein is intended for use within the framework
   of the "multipart/report" content type defined in [2].

   This memo defines only the format of the notifications.  An extension
   to the Simple Message Transfer Protocol (SMTP) [3] to fully support
   such notifications is the subject of a separate memo [4].

1.1 Purposes

   The DSNs defined in this memo are expected to serve several purposes:

(a) Inform human beings of the status of message delivery processing, as
    well as the reasons for any delivery problems or outright failures,
    in a manner which is largely independent of human language;

(b) Allow mail user agents to keep track of the delivery status of
    messages sent, by associating returned DSNs with earlier message
    transmissions;

(c) Allow mailing list exploders to automatically maintain their
    subscriber lists when delivery attempts repeatedly fail;

(d) Convey delivery and non-delivery notifications resulting from
    attempts to deliver messages to "foreign" mail systems via a
    gateway;

(e) Allow "foreign" notifications to be tunneled through a MIME-capable
    message system and back into the original messaging system that
    issued the original notification, or even to a third messaging
    system;

(f) Allow language-independent, yet reasonably precise, indications of
    the reason for the failure of a message to be delivered (once status
    codes of sufficient precision are defined); and

(g) Provide sufficient information to remote MTA maintainers (via
    "trouble tickets") so that they can understand the nature of
    reported errors.  This feature is used in the case that failure to
    deliver a message is due to the malfunction of a remote MTA and the



Moore & Vaudreuil           Standards Track                     [Page 2]

RFC 1894             Delivery Status Notifications          January 1996


    sender wants to report the problem to the remote MTA administrator.

1.2 Requirements

    These purposes place the following constraints on the notification
    protocol:

(a) It must be readable by humans as well as being machine-parsable.

(b) It must provide enough information to allow message senders (or the
    user agents) to unambiguously associate a DSN with the message that
    was sent and the original recipient address for which the DSN is
    issued (if such information is available), even if the message was
    forwarded to another recipient address.

(c) It must be able to preserve the reason for the success or failure of
    a delivery attempt in a remote messaging system, using the
    "language" (mailbox addresses and status codes) of that remote
    system.

(d) It must also be able to describe the reason for the success or
    failure of a delivery attempt, independent of any particular human
    language or of the "language" of any particular mail system.

(e) It must preserve enough information to allow the maintainer of a
    remote MTA to understand (and if possible, reproduce) the conditions
    that caused a delivery failure at that MTA.

(f) For any notifications issued by foreign mail systems, which are
    translated by a mail gateway to the DSN format, the DSN must
    preserve the "type" of the foreign addresses and error codes, so
    that these may be correctly interpreted by gateways.

   A DSN contains a set of per-message fields which identify the message
   and the transaction during which the message was submitted, along
   with other fields that apply to all delivery attempts described by
   the DSN.  The DSN also includes a set of per-recipient fields to
   convey the result of the attempt to deliver the message to each of
   one or more recipients.

1.3 Terminology

   A message may be transmitted through several message transfer agents
   (MTAs) on its way to a recipient.  For a variety of reasons,
   recipient addresses may be rewritten during this process, so each MTA
   may potentially see a different recipient address.  Depending on the
   purpose for which a DSN is used, different formats of a particular
   recipient address will be needed.



Moore & Vaudreuil           Standards Track                     [Page 3]

RFC 1894             Delivery Status Notifications          January 1996


   Several DSN fields are defined in terms of the view from a particular
   MTA in the transmission.  The MTAs are assigned the following names:

   (a) Original MTA

   The Original MTA is the one to which the message is submitted for
   delivery by the sender of the message.

   (b) Reporting MTA

   For any DSN, the Reporting MTA is the one which is reporting the
   results of delivery attempts described in the DSN.

   If the delivery attempts described occurred in a "foreign" (non-
   Internet) mail system, and the DSN was produced by translating the
   foreign notice into DSN format, the Reporting MTA will still identify
   the "foreign" MTA where the delivery attempts occurred.

   (c) Received-From MTA

   The Received-From MTA is the MTA from which the Reporting MTA
   received the message, and accepted responsibility for delivery of the
   message.

   (d) Remote MTA

   If an MTA determines that it must relay a message to one or more
   recipients, but the message cannot be transferred to its "next hop"
   MTA, or if the "next hop" MTA refuses to accept responsibility for
   delivery of the message to one or more of its intended recipients,
   the relaying MTA may need to issue a DSN on behalf of the recipients
   for whom the message cannot be delivered.  In this case the relaying
   MTA is the Reporting MTA, and the "next hop" MTA is known as the
   Remote MTA.

















Moore & Vaudreuil           Standards Track                     [Page 4]

RFC 1894             Delivery Status Notifications          January 1996


Figure 1 illustrates the relationship between the various MTAs.


+-----+    +--------+           +---------+    +---------+      +------+
|     |    |        |           |Received-|    |         |      |      |
|     | => |Original| => ... => |  From   | => |Reporting| ===> |Remote|
| user|    |   MTA  |           |   MTA   |    |   MTA   | <No! |  MTA |
|agent|    +--------+           +---------+    +----v----+      +------+
|     |                                             |
|     | <-------------------------------------------+
+-----+      (DSN returned to sender by Reporting MTA)


     Figure 1.  Original, Received-From, Reporting and Remote MTAs


   Each of these MTAs may provide information which is useful in a DSN:

+ Ideally, the DSN will contain the address of each recipient as
  originally specified to the Original MTA by the sender of the message.
  This version of the address is needed (rather than a forwarding
  address or some modified version of the original address) so that the
  sender may compare the recipient address in the DSN with the address
  in the sender's records (e.g. an address book for an individual, the
  list of subscribers for a mailing list) and take appropriate action.

  Similarly, the DSN might contain an "envelope identifier" that was
  known to both the sender's user agent and the Original MTA at the time
  of message submission, and which, if included in the DSN, can be used
  by the sender to keep track of which messages were or were not
  delivered.

+ If a message was (a) forwarded to a different address than that
  specified by the sender, (b) gatewayed to a different mail system than
  that used by the sender, or (c) subjected to address rewriting during
  transmission, the "final" form of the recipient address (i.e. the one
  seen by the Reporting MTA) will be different than the original
  (sender-specified) recipient address.  Just as the sender's user agent
  (or the sender) prefers the original recipient address, so the "final"
  address is needed when reporting a problem to the postmaster of the
  site where message delivery failed, because only the final recipient
  address will allow her to reproduce the conditions that caused the
  failure.

+ A "failed" DSN should contain the most accurate explanation for the
  delivery failure that is available.  For ease of interpretation, this
  information should be a format which is independent of the mail
  transport system that issued the DSN.  However, if a foreign error



Moore & Vaudreuil           Standards Track                     [Page 5]

RFC 1894             Delivery Status Notifications          January 1996


  code is translated into some transport-independent format, some
  information may be lost.  It is therefore desirable to provide both a
  transport-independent status code and a mechanism for reporting
  transport-specific codes.  Depending on the circumstances that
  produced delivery failure, the transport-specific code might be
  obtained from either the Reporting MTA or the Remote MTA.

   Since different values for "recipient address" and "delivery status
   code" are needed according to the circumstance in which a DSN will be
   used, and since the MTA that issues the DSN cannot anticipate those
   circumstances, the DSN format described here may contain both the
   original and final forms of a recipient address, and both a
   transport-independent and a transport-specific indication of delivery
   status.

   Extension fields may also be added by the Reporting MTA as needed to
   provide additional information for use in a trouble ticket or to
   preserve information for tunneling of foreign delivery reports
   through Internet DSNs.

   The Original, Reporting, and Remote MTAs may exist in very different
   environments and use dissimilar transport protocols, MTA names,
   address formats, and delivery status codes.  DSNs therefore do not
   assume any particular format for mailbox addresses, MTA names, or
   transport-specific status codes.  Instead, the various DSN fields
   that carry such quantities consist of a "type" subfield followed by a
   subfield whose contents are ordinary text characters, and the format
   of which is indicated by the "type" subfield.  This allows a DSN to
   convey these quantities regardless of format.

2. Format of a Delivery Status Notification

   A DSN is a MIME message with a top-level content-type of
   multipart/report (defined in [2]).  When a multipart/report content
   is used to transmit a DSN:

(a) The report-type parameter of the multipart/report content is
    "delivery-status".

(b) The first component of the multipart/report contains a human-
    readable explanation of the DSN, as described in [2].

(c) The second component of the multipart/report is of content-type
    message/delivery-status, described in section 2.1 of this document.

(d) If the original message or a portion of the message is to be
    returned to the sender, it appears as the third component of the
    multipart/report.



Moore & Vaudreuil           Standards Track                     [Page 6]

RFC 1894             Delivery Status Notifications          January 1996


    NOTE: For delivery status notifications gatewayed from foreign
    systems, the headers of the original message may not be available.
    In this case the third component of the DSN may be omitted, or it
    may contain "simulated" RFC 822 headers which contain equivalent
    information.  In particular, it is very desirable to preserve the
    subject, date, and message-id (or equivalent) fields from the
    original message.

   The DSN MUST be addressed (in both the message header and the
   transport envelope) to the return address from the transport envelope
   which accompanied the original message for which the DSN was
   generated.  (For a message that arrived via SMTP, the envelope return
   address appears in the MAIL FROM command.)

   The From field of the message header of the DSN SHOULD contain the
   address of a human who is responsible for maintaining the mail system
   at the Reporting MTA site (e.g.  Postmaster), so that a reply to the
   DSN will reach that person.  Exception: if a DSN is translated from a
   foreign delivery report, and the gateway performing the translation
   cannot determine the appropriate address, the From field of the DSN
   MAY be the address of a human who is responsible for maintaining the
   gateway.

   The envelope sender address of the DSN SHOULD be chosen to ensure
   that no delivery status reports will be issued in response to the DSN
   itself, and MUST be chosen so that DSNs will not generate mail loops.
   Whenever an SMTP transaction is used to send a DSN, the MAIL FROM
   command MUST use a NULL return address, i.e. "MAIL FROM:<>".

   A particular DSN describes the delivery status for exactly one
   message.  However, an MTA MAY report on the delivery status for
   several recipients of the same message in a single DSN.  Due to the
   nature of the mail transport system (where responsibility for
   delivery of a message to its recipients may be split among several
   MTAs, and delivery to any particular recipient may be delayed),
   multiple DSNs may be still be issued in response to a single message
   submission.














Moore & Vaudreuil           Standards Track                     [Page 7]

RFC 1894             Delivery Status Notifications          January 1996


2.1 The message/delivery-status content-type

   The message/delivery-status content-type is defined as follows:

     MIME type name:                message
     MIME subtype name:             delivery-status
     Optional parameters:           none
     Encoding considerations:       "7bit" encoding is sufficient and
                                    MUST be used to maintain readability
                                    when viewed by non-MIME mail
                                    readers.
     Security considerations:       discussed in section 4 of this memo.

   The message/delivery-status report type for use in the
   multipart/report is "delivery-status".

   The body of a message/delivery-status consists of one or more
   "fields" formatted according to the ABNF of RFC 822 header "fields"
   (see [6]).  The per-message fields appear first, followed by a blank
   line.  Following the per-message fields are one or more groups of
   per-recipient fields.  Each group of per-recipient fields is preceded
   by a blank line.  Using the ABNF of RFC 822, the syntax of the
   message/delivery-status content is as follows:

     delivery-status-content =
          per-message-fields 1*( CRLF per-recipient-fields )

   The per-message fields are described in section 2.2.  The per-
   recipient fields are described in section 2.3.


2.1.1 General conventions for DSN fields

   Since these fields are defined according to the rules of RFC 822, the
   same conventions for continuation lines and comments apply.
   Notification fields may be continued onto multiple lines by beginning
   each additional line with a SPACE or HTAB.  Text which appears in
   parentheses is considered a comment and not part of the contents of
   that notification field.  Field names are case-insensitive, so the
   names of notification fields may be spelled in any combination of
   upper and lower case letters.  Comments in DSN fields may use the
   "encoded-word" construct defined in [7].

   A number of DSN fields are defined to have a portion of a field body
   of "xtext".  "xtext" is used to allow encoding sequences of octets
   which contain values outside the range [1-127 decimal] of traditional
   ASCII characters, and also to allow comments to be inserted in the
   data.  Any octet may be encoded as "+" followed by two upper case



Moore & Vaudreuil           Standards Track                     [Page 8]

RFC 1894             Delivery Status Notifications          January 1996


   hexadecimal digits.  (The "+" character MUST be encoded as "+2B".)
   With certain exceptions, octets that correspond to ASCII characters
   may be represented as themselves.  SPACE and HTAB characters are
   ignored.  Comments may be included by enclosing them in parenthesis.
   Except within comments, encoded-words such as defined in [7] may NOT
   be used in xtext.

   "xtext" is formally defined as follows:

     xtext = *( xchar / hexchar / linear-white-space / comment )

     xchar = any ASCII CHAR between "!" (33) and "~" (126) inclusive,
          except for "+", "\" and "(".

   "hexchar"s are intended to encode octets that cannot be represented
   as plain text, either because they are reserved, or because they are
   non-printable.  However, any octet value may be represented by a
   "hexchar".

     hexchar = ASCII "+" immediately followed by two upper case
          hexadecimal digits

   When encoding an octet sequence as xtext:

   + Any ASCII CHAR between "!" and "~" inclusive, except for "+", "\",
     and "(", MAY be encoded as itself.  (Some CHARs in this range may
     also be encoded as "hexchar"s, at the implementor's discretion.)

   + ASCII CHARs that fall outside the range above must be encoded as
     "hexchar".

   + Line breaks (CR LF SPACE) MAY be inserted as necessary to keep line
     lengths from becoming excessive.

   + Comments MAY be added to clarify the meaning for human readers.

2.1.2 "*-type" subfields

   Several DSN fields consist of a "-type" subfield, followed by a
   semicolon, followed by "*text".  For these fields, the keyword used
   in the address-type, diagnostic-type, or MTA-name-type subfield
   indicates the expected format of the address, status-code, or MTA-
   name which follows.








Moore & Vaudreuil           Standards Track                     [Page 9]

RFC 1894             Delivery Status Notifications          January 1996


   The "-type" subfields are defined as follows:

(a) An "address-type" specifies the format of a mailbox address.  For
    example, Internet mail addresses use the "rfc822" address-type.

         address-type = atom

(b) A "diagnostic-type" specifies the format of a status code.  For
    example, when a DSN field contains a reply code reported via the
    Simple Mail Transfer Protocol [3], the "smtp" diagnostic-type is
    used.

         diagnostic-type = atom

(c) An "MTA-name-type" specifies the format of an MTA name.  For
    example, for an SMTP server on an Internet host, the MTA name is the
    domain name of that host, and the "dns" MTA-name-type is used.

         mta-name-type = atom

   Values for address-type, diagnostic-type, and MTA-name-type are
   case-insensitive.  Thus address-type values of "RFC822" and "rfc822"
   are equivalent.

   The Internet Assigned Numbers Authority (IANA) will maintain a
   registry of address-types, diagnostic-types, and MTA-name-types,
   along with descriptions of the meanings and acceptable values of
   each, or a reference to a one or more specifications that provide
   such descriptions.  (The "rfc822" address-type, "smtp" diagnostic-
   type, and "dns" MTA-name-type are defined in [4].)  Registration
   forms for address-type, diagnostic-type, and MTA-name-type appear in
   section 8 of this document.

   IANA will not accept registrations for any address-type, diagnostic-
   type, or MTA-name-type name that begins with "X-".  These type names
   are reserved for experimental use.

2.1.3 Lexical tokens imported from RFC 822

   The following lexical tokens, defined in [6], are used in the ABNF
   grammar for DSNs: atom, CHAR, comment, CR, CRLF, DIGIT, LF, linear-
   white-space, SPACE, text.  The date-time lexical token is defined in
   [8].








Moore & Vaudreuil           Standards Track                    [Page 10]

RFC 1894             Delivery Status Notifications          January 1996


2.2 Per-Message DSN Fields

   Some fields of a DSN apply to all of the delivery attempts described
   by that DSN.  These fields may appear at most once in any DSN.  These
   fields are used to correlate the DSN with the original message
   transaction and to provide additional information which may be useful
   to gateways.

     per-message-fields =
          [ original-envelope-id-field CRLF ]
          reporting-mta-field CRLF
          [ dsn-gateway-field CRLF ]
          [ received-from-mta-field CRLF ]
          [ arrival-date-field CRLF ]
          *( extension-field CRLF )

2.2.1 The Original-Envelope-Id field

   The optional Original-Envelope-Id field contains an "envelope
   identifier" which uniquely identifies the transaction during which
   the message was submitted, and was either (a) specified by the sender
   and supplied to the sender's MTA, or (b) generated by the sender's
   MTA and made available to the sender when the message was submitted.
   Its purpose is to allow the sender (or her user agent) to associate
   the returned DSN with the specific transaction in which the message
   was sent.

   If such an envelope identifier was present in the envelope which
   accompanied the message when it arrived at the Reporting MTA, it
   SHOULD be supplied in the Original-Envelope-Id field of any DSNs
   issued as a result of an attempt to deliver the message.  Except when
   a DSN is issued by the sender's MTA, an MTA MUST NOT supply this
   field unless there is an envelope-identifier field in the envelope
   which accompanied this message on its arrival at the Reporting MTA.

   The Original-Envelope-Id field is defined as follows:

     original-envelope-id-field =
          "Original-Envelope-Id" ":" envelope-id

     envelope-id = *text

   There may be at most one Original-Envelope-Id field per DSN.

   The envelope-id is CASE-SENSITIVE.  The DSN MUST preserve the
   original case and spelling of the envelope-id.





Moore & Vaudreuil           Standards Track                    [Page 11]

RFC 1894             Delivery Status Notifications          January 1996


   NOTE: The Original-Envelope-Id is NOT the same as the Message-Id from
   the message header.  The Message-Id identifies the content of the
   message, while the Original-Envelope-Id identifies the transaction in
   which the message is sent.

2.2.2 The Reporting-MTA DSN field

     reporting-mta-field =
          "Reporting-MTA" ":" mta-name-type ";" mta-name

     mta-name = *text

   The Reporting-MTA field is defined as follows:

   A DSN describes the results of attempts to deliver, relay, or gateway
   a message to one or more recipients.  In all cases, the Reporting-MTA
   is the MTA which attempted to perform the delivery, relay, or gateway
   operation described in the DSN.  This field is required.

   Note that if an SMTP client attempts to relay a message to an SMTP
   server and receives an error reply to a RCPT command, the client is
   responsible for generating the DSN, and the client's domain name will
   appear in the Reporting-MTA field.  (The server's domain name will
   appear in the Remote-MTA field.)

   Note that the Reporting-MTA is not necessarily the MTA which actually
   issued the DSN.  For example, if an attempt to deliver a message
   outside of the Internet resulted in a nondelivery notification which
   was gatewayed back into Internet mail, the Reporting-MTA field of the
   resulting DSN would be that of the MTA that originally reported the
   delivery failure, not that of the gateway which converted the foreign
   notification into a DSN.  See Figure 2.



















Moore & Vaudreuil           Standards Track                    [Page 12]

RFC 1894             Delivery Status Notifications          January 1996


sender's environment                            recipient's environment
............................ ..........................................
                           : :
                       (1) : :                             (2)
  +-----+  +--------+  +--------+  +---------+  +---------+   +------+
  |     |  |        |  |        |  |Received-|  |         |   |      |
  |     |=>|Original|=>|        |->|  From   |->|Reporting|-->|Remote|
  | user|  |   MTA  |  |        |  |   MTA   |  |   MTA   |<No|  MTA |
  |agent|  +--------+  |Gateway |  +---------+  +----v----+   +------+
  |     |              |        |                    |
  |     | <============|        |<-------------------+
  +-----+              |        |(4)                (3)
                       +--------+
                           : :
...........................: :.........................................

              Figure 2.  DSNs in the presence of gateways

     (1) message is gatewayed into recipient's environment
     (2) attempt to relay message fails
     (3) reporting-mta (in recipient's environment) returns nondelivery
         notification
     (4) gateway translates foreign notification into a DSN



   The mta-name portion of the Reporting-MTA field is formatted
   according to the conventions indicated by the mta-name-type subfield.
   If an MTA functions as a gateway between dissimilar mail environments
   and thus is known by multiple names depending on the environment, the
   mta-name subfield SHOULD contain the name used by the environment
   from which the message was accepted by the Reporting-MTA.

   Because the exact spelling of an MTA name may be significant in a
   particular environment, MTA names are CASE-SENSITIVE.

2.2.3 The DSN-Gateway field

   The DSN-Gateway field indicates the name of the gateway or MTA which
   translated a foreign (non-Internet) delivery status notification into
   this DSN.  This field MUST appear in any DSN which was translated by
   a gateway from a foreign system into DSN format, and MUST NOT appear
   otherwise.

   dsn-gateway-field = "DSN-Gateway" ":" mta-name-type ";" mta-name






Moore & Vaudreuil           Standards Track                    [Page 13]

RFC 1894             Delivery Status Notifications          January 1996


   For gateways into Internet mail, the MTA-name-type will normally be
   "smtp", and the mta-name will be the Internet domain name of the
   gateway.

2.2.4 The Received-From-MTA DSN field

   The optional Received-From-MTA field indicates the name of the MTA
   from which the message was received.

     received-from-mta-field =
          "Received-From-MTA" ":" mta-name-type ";" mta-name

   If the message was received from an Internet host via SMTP, the
   contents of the mta-name subfield SHOULD be the Internet domain name
   supplied in the HELO or EHLO command, and the network address used by
   the SMTP client SHOULD be included as a comment enclosed in
   parentheses.  (In this case, the MTA-name-type will be "smtp".)

   The mta-name portion of the Received-From-MTA field is formatted
   according to the conventions indicated by the MTA-name-type subfield.

   Since case is significant in some mail systems, the exact spelling,
   including case, of the MTA name SHOULD be preserved.

2.2.5 The Arrival-Date DSN field

   The optional Arrival-Date field indicates the date and time at which
   the message arrived at the Reporting MTA.  If the Last-Attempt-Date
   field is also provided in a per-recipient field, this can be used to
   determine the interval between when the message arrived at the
   Reporting MTA and when the report was issued for that recipient.

     arrival-date-field = "Arrival-Date" ":" date-time

   The date and time are expressed in RFC 822 'date-time' format, as
   modified by [8].  Numeric timezones ([+/-]HHMM format) MUST be used.

2.3 Per-Recipient DSN fields

   A DSN contains information about attempts to deliver a message to one
   or more recipients.  The delivery information for any particular
   recipient is contained in a group of contiguous per-recipient fields.
   Each group of per-recipient fields is preceded by a blank line.








Moore & Vaudreuil           Standards Track                    [Page 14]

RFC 1894             Delivery Status Notifications          January 1996


   The syntax for the group of per-recipient fields is as follows:


     per-recipient-fields =
          [ original-recipient-field CRLF ]
          final-recipient-field CRLF
          action-field CRLF
          status-field CRLF
          [ remote-mta-field CRLF ]
          [ diagnostic-code-field CRLF ]
          [ last-attempt-date-field CRLF ]
          [ will-retry-until-field CRLF ]
          *( extension-field CRLF )

2.3.1 Original-Recipient field

   The Original-Recipient field indicates the original recipient address
   as specified by the sender of the message for which the DSN is being
   issued.

     original-recipient-field =
          "Original-Recipient" ":" address-type ";" generic-address

     generic-address = *text

   The address-type field indicates the type of the original recipient
   address.  If the message originated within the Internet, the
   address-type field field will normally be "rfc822", and the address
   will be according to the syntax specified in [6].  The value
   "unknown" should be used if the Reporting MTA cannot determine the
   type of the original recipient address from the message envelope.

   This field is optional.  It should be included only if the sender-
   specified recipient address was present in the message envelope, such
   as by the SMTP extensions defined in [4].  This address is the same
   as that provided by the sender and can be used to automatically
   correlate DSN reports and message transactions.

2.3.2 Final-Recipient field

   The Final-Recipient field indicates the recipient for which this set
   of per-recipient fields applies.  This field MUST be present in each
   set of per-recipient data.








Moore & Vaudreuil           Standards Track                    [Page 15]

RFC 1894             Delivery Status Notifications          January 1996


   The syntax of the field is as follows:

     final-recipient-field =
          "Final-Recipient" ":" address-type ";" generic-address

   The generic-address subfield of the Final-Recipient field MUST
   contain the mailbox address of the recipient (from the transport
   envelope) as it was when the message was accepted for delivery by the
   Reporting MTA.

   The Final-Recipient address may differ from the address originally
   provided by the sender, because it may have been transformed during
   forwarding and gatewaying into an totally unrecognizable mess.
   However, in the absence of the optional Original-Recipient field, the
   Final-Recipient field and any returned content may be the only
   information available with which to correlate the DSN with a
   particular message submission.

   The address-type subfield indicates the type of address expected by
   the reporting MTA in that context.  Recipient addresses obtained via
   SMTP will normally be of address-type "rfc822".

   NOTE: The Reporting MTA is not expected to ensure that the address
   actually conforms to the syntax conventions of the address-type.
   Instead, it MUST report exactly the address received in the envelope,
   unless that address contains characters such as CR or LF which may
   not appear in a DSN field.

   Since mailbox addresses (including those used in the Internet) may be
   case sensitive, the case of alphabetic characters in the address MUST
   be preserved.

2.3.3 Action field

   The Action field indicates the action performed by the Reporting-MTA
   as a result of its attempt to deliver the message to this recipient
   address.  This field MUST be present for each recipient named in the
   DSN.

   The syntax for the action-field is:

     action-field = "Action" ":" action-value

     action-value =
          "failed" / "delayed" / "delivered" / "relayed" / "expanded"






Moore & Vaudreuil           Standards Track                    [Page 16]

RFC 1894             Delivery Status Notifications          January 1996


   The action-value may be spelled in any combination of upper and lower
   case characters.

"failed"     indicates that the message could not be delivered to the
             recipient.  The Reporting MTA has abandoned any attempts to
             deliver the message to this recipient.  No further
             notifications should be expected.

"delayed"    indicates that the Reporting MTA has so far been unable to
             deliver or relay the message, but it will continue to
             attempt to do so.  Additional notification messages may be
             issued as the message is further delayed or successfully
             delivered, or if delivery attempts are later abandoned.

"delivered"  indicates that the message was successfully delivered to
             the recipient address specified by the sender, which
             includes "delivery" to a mailing list exploder.  It does
             not indicate that the message has been read.  This is a
             terminal state and no further DSN for this recipient should
             be expected.

"relayed"    indicates that the message has been relayed or gatewayed
             into an environment that does not accept responsibility for
             generating DSNs upon successful delivery.  This action-
             value SHOULD NOT be used unless the sender has requested
             notification of successful delivery for this recipient.

"expanded"   indicates that the message has been successfully delivered
             to the recipient address as specified by the sender, and
             forwarded by the Reporting-MTA beyond that destination to
             multiple additional recipient addresses.  An action-value
             of "expanded" differs from "delivered" in that "expanded"
             is not a terminal state. Further "failed" and/or "delayed"
             notifications may be provided.

             Using the terms "mailing list" and "alias" as defined in
             [4], section 7.2.7:  An action-value of "expanded" is only
             to be used when the message is delivered to a multiple-
             recipient "alias".  An action-value of "expanded" SHOULD
             NOT be used with a DSN issued on delivery of a message to a
             "mailing list".

   NOTE ON ACTION VS. STATUS CODES:  Although the 'action' field might
   seem to be redundant with the 'status' field, this is not the case.
   In particular, a "temporary failure" ("4") status code could be used
   with an action-value of either "delayed" or "failed".  For example,
   assume that an SMTP client repeatedly tries to relay a message to the
   mail exchanger for a recipient, but fails because a query to a domain



Moore & Vaudreuil           Standards Track                    [Page 17]

RFC 1894             Delivery Status Notifications          January 1996


   name server timed out.  After a few hours, it might issue a "delayed"
   DSN to inform the sender that the message had not yet been delivered.
   After a few days, the MTA might abandon its attempt to deliver the
   message and return a "failed" DSN.  The status code (which would
   begin with a "4" to indicate "temporary failure") would be the same
   for both DSNs.

   Another example for which the action and status codes may appear
   contradictory:  If an MTA or mail gateway cannot deliver a message
   because doing so would entail conversions resulting in an
   unacceptable loss of information, it would issue a DSN with the
   'action' field of "failure" and a status code of 'XXX'.  If the
   message had instead been relayed, but with some loss of information,
   it might generate a DSN with the same XXX status-code, but with an
   action field of "relayed".

2.3.4 Status field

   The per-recipient Status field contains a transport-independent
   status code which indicates the delivery status of the message to
   that recipient.  This field MUST be present for each delivery attempt
   which is described by a DSN.

   The syntax of the status field is:

     status-field = "Status" ":" status-code

     status-code = DIGIT "." 1*3DIGIT "." 1*3DIGIT

          ; White-space characters and comments are NOT allowed within a
          ; status-code, though a comment enclosed in parentheses MAY follow
          ; the last numeric subfield of the status-code.  Each numeric
          ; subfield within the status-code MUST be expressed without
          ; leading zero digits.

   Status codes thus consist of three numerical fields separated by ".".
   The first sub-field indicates whether the delivery attempt was
   successful (2 = success, 4 = persistent temporary failure, 5 =
   permanent failure).  The second sub-field indicates the probable
   source of any delivery anomalies, and the third sub-field denotes a
   precise error condition, if known.

   The initial set of status-codes is defined in [5].








Moore & Vaudreuil           Standards Track                    [Page 18]

RFC 1894             Delivery Status Notifications          January 1996


2.3.5 Remote-MTA field

   The value associated with the Remote-MTA DSN field is a printable
   ASCII representation of the name of the "remote" MTA that reported
   delivery status to the "reporting" MTA.

     remote-mta-field = "Remote-MTA" ":" mta-name-type ";" mta-name

   NOTE: The Remote-MTA field preserves the "while talking to"
   information that was provided in some pre-existing nondelivery
   reports.

   This field is optional.  It MUST NOT be included if no remote MTA was
   involved in the attempted delivery of the message to that recipient.

2.3.6 Diagnostic-Code field

   For a "failed" or "delayed" recipient, the Diagnostic-Code DSN field
   contains the actual diagnostic code issued by the mail transport.
   Since such codes vary from one mail transport to another, the
   diagnostic-type subfield is needed to specify which type of
   diagnostic code is represented.

     diagnostic-code-field =
          "Diagnostic-Code" ":" diagnostic-type ";" *text

   NOTE:  The information in the Diagnostic-Code field may be somewhat
   redundant with that from the Status field.  The Status field is
   needed so that any DSN, regardless of origin, may be understood by
   any user agent or gateway that parses DSNs.  Since the Status code
   will sometimes be less precise than the actual transport diagnostic
   code, the Diagnostic-Code field is provided to retain the latter
   information.  Such information may be useful in a trouble ticket sent
   to the administrator of the Reporting MTA, or when tunneling foreign
   nondelivery reports through DSNs.

   If the Diagnostic Code was obtained from a Remote MTA during an
   attempt to relay the message to that MTA, the Remote-MTA field should
   be present.  When interpreting a DSN, the presence of a Remote-MTA
   field indicates that the Diagnostic Code was issued by the Remote
   MTA.  The absence of a Remote-MTA indicates that the Diagnostic Code
   was issued by the Reporting MTA.

   In addition to the Diagnostic-Code itself, additional textual
   description of the diagnostic, MAY appear in a comment enclosed in
   parentheses.





Moore & Vaudreuil           Standards Track                    [Page 19]

RFC 1894             Delivery Status Notifications          January 1996


   This field is optional, because some mail systems supply no
   additional information beyond that which is returned in the 'action'
   and 'status' fields.  However, this field SHOULD be included if
   transport-specific diagnostic information is available.

2.3.7 Last-Attempt-Date field

   The Last-Attempt-Date field gives the date and time of the last
   attempt to relay, gateway, or deliver the message (whether successful
   or unsuccessful) by the Reporting MTA.  This is not necessarily the
   same as the value of the Date field from the header of the message
   used to transmit this delivery status notification: In cases where
   the DSN was generated by a gateway, the Date field in the message
   header contains the time the DSN was sent by the gateway and the DSN
   Last-Attempt-Date field contains the time the last delivery attempt
   occurred.

     last-attempt-date-field = "Last-Attempt-Date" ":" date-time

   This field is optional.  It MUST NOT be included if the actual date
   and time of the last delivery attempt are not available (which might
   be the case if the DSN were being issued by a gateway).

   The date and time are expressed in RFC 822 'date-time' format, as
   modified by [8].  Numeric timezones ([+/-]HHMM format) MUST be used.

   3.2.1.5 final-log-id field

   The "final-log-id" field gives the final-log-id of the message that
   was used by the final-mta.  This can be useful as an index to the
   final-mta's log entry for that delivery attempt.

     final-log-id-field = "Final-Log-ID" ":" *text

   This field is optional.

2.3.8 Will-Retry-Until field

   For DSNs of type "delayed", the Will-Retry-Until field gives the date
   after which the Reporting MTA expects to abandon all attempts to
   deliver the message to that recipient.  The Will-Retry-Until field is
   optional for "delay" DSNs, and MUST NOT appear in other DSNs.

     will-retry-until-field = "Will-Retry-Until" ":" date-time

   The date and time are expressed in RFC 822 'date-time' format, as
   modified by [8].  Numeric timezones ([+/-]HHMM format) MUST be used.




Moore & Vaudreuil           Standards Track                    [Page 20]

RFC 1894             Delivery Status Notifications          January 1996


2.4 Extension fields

   Additional per-message or per-recipient DSN fields may be defined in
   the future by later revisions or extensions to this specification.
   Extension-field names beginning with "X-" will never be defined as
   standard fields; such names are reserved for experimental use.  DSN
   field names NOT beginning with "X-" MUST be registered with the
   Internet Assigned Numbers Authority (IANA) and published in an RFC.

   Extension DSN fields may be defined for the following reasons:

   (a) To allow additional information from foreign delivery status
       reports to be tunneled through Internet DSNs.  The names of such
       DSN fields should begin with an indication of the foreign
       environment name (e.g.  X400-Physical-Forwarding-Address).

   (b) To allow the transmission of diagnostic information which is
       specific to a particular mail transport protocol.  The names of
       such DSN fields should begin with an indication of the mail
       transport being used (e.g. SMTP-Remote-Recipient-Address).  Such
       fields should be used for diagnostic purposes only and not by
       user agents or mail gateways.

   (c) To allow transmission of diagnostic information which is specific
       to a particular message transfer agent (MTA).  The names of such
       DSN fields should begin with an indication of the MTA
       implementation which produced the DSN.  (e.g. Foomail-Queue-ID).

   MTA implementors are encouraged to provide adequate information, via
   extension fields if necessary, to allow an MTA maintainer to
   understand the nature of correctable delivery failures and how to fix
   them.  For example, if message delivery attempts are logged, the DSN
   might include information which allows the MTA maintainer to easily
   find the log entry for a failed delivery attempt.

   If an MTA developer does not wish to register the meanings of such
   extension fields, "X-" fields may be used for this purpose.  To avoid
   name collisions, the name of the MTA implementation should follow the
   "X-", (e.g.  "X-Foomail-Log-ID").

3. Conformance and Usage Requirements

   An MTA or gateway conforms to this specification if it generates DSNs
   according to the protocol defined in this memo.  For MTAs and
   gateways that do not support requests for positive delivery
   notification (such as in [4]), it is sufficient that delivery failure
   reports use this protocol.




Moore & Vaudreuil           Standards Track                    [Page 21]

RFC 1894             Delivery Status Notifications          January 1996


   A minimal implementation of this specification need generate only the
   Reporting-MTA per-message field, and the Final-Recipient, Action, and
   Status fields for each attempt to deliver a message to a recipient
   described by the DSN.  Generation of the other fields, when
   appropriate, is strongly recommended.

   MTAs and gateways MUST NOT generate the Original-Recipient field of a
   DSN unless the mail transfer protocol provides the address originally
   specified by the sender at the time of submission. (Ordinary SMTP
   does not make that guarantee, but the SMTP extension defined in [4]
   permits such information to be carried in the envelope if it is
   available.)

   Each sender-specified recipient address SHOULD result in at most one
   "delivered" or "failed" DSN for that recipient.  If a positive DSN is
   requested (e.g. one using NOTIFY=SUCCESS in SMTP) for a recipient
   that is forwarded to multiple recipients of an "alias" (as defined in
   [4], section 7.2.7), the forwarding MTA SHOULD normally issue a
   "expanded" DSN for the originally-specified recipient and not
   propagate the request for a DSN to the forwarding addresses.
   Alternatively, the forwarding MTA MAY relay the request for a DSN to
   exactly one of the forwarding addresses and not propagate the request
   to the others.

   By contrast, successful submission of a message to a mailing list
   exploder is considered final delivery of the message.  Upon delivery
   of a message to a recipient address corresponding to a mailing list
   exploder, the Reporting MTA SHOULD issue an appropriate DSN exactly
   as if the recipient address were that of an ordinary mailbox.

   NOTE:  This is actually intended to make DSNs usable by mailing lists
   themselves.  Any message sent to a mailing list subscriber should
   have its envelope return address pointing to the list maintainer [see
   RFC 1123, section 5.3.7(E)].  Since DSNs are sent to the envelope
   return address, all DSNs resulting from delivery to the recipients of
   a mailing list will be sent to the list maintainer.  The list
   maintainer may elect to mechanically process DSNs upon receipt, and
   thus automatically delete invalid addresses from the list.  (See
   section 7 of this memo.)

   This specification places no restrictions on the processing of DSNs
   received by user agents or distribution lists.

4. Security Considerations

   The following security considerations apply when using DSNs:





Moore & Vaudreuil           Standards Track                    [Page 22]

RFC 1894             Delivery Status Notifications          January 1996


4.1 Forgery

   DSNs may be forged as easily as ordinary Internet electronic mail.
   User agents and automatic mail handling facilities (such as mail
   distribution list exploders) that wish to make automatic use of DSNs
   should take appropriate precautions to minimize the potential damage
   from denial-of-service attacks.

   Security threats related to forged DSNs include the sending of:

(a) A falsified delivery notification when the message is not delivered
    to the indicated recipient,
(b) A falsified non-delivery notification when the message was in fact
    delivered to the indicated recipient,
(c) A falsified Final-Recipient address,
(d) A falsified Remote-MTA identification,
(e) A falsified relay notification when the message is "dead ended".
(f) Unsolicited DSNs

4.2 Confidentiality

   Another dimension of security is confidentiality.  There may be cases
   in which a message recipient is autoforwarding messages but does not
   wish to divulge the address to which the messages are autoforwarded.
   The desire for such confidentiality will probably be heightened as
   "wireless mailboxes", such as pagers, become more widely used as
   autoforward addresses.

   MTA authors are encouraged to provide a mechanism which enables the
   end user to preserve the confidentiality of a forwarding address.
   Depending on the degree of confidentiality required, and the nature
   of the environment to which a message were being forwarded, this
   might be accomplished by one or more of:

(a) issuing a "relayed" DSN (if a positive DSN was requested) when a
    message is forwarded to a confidential forwarding address, and
    disabling requests for positive DSNs for the forwarded message,

(b) declaring the message to be delivered, issuing a "delivered" DSN,
    re-sending the message to the confidential forwarding address, and
    arranging for no DSNs to be issued for the re-sent message,

(c) omitting "Remote-*" or extension fields of a DSN whenever they would
    otherwise contain confidential information (such as a confidential
    forwarding address),

(d) for messages forwarded to a confidential address, setting the
    envelope return address (e.g. SMTP MAIL FROM address) to the NULL



Moore & Vaudreuil           Standards Track                    [Page 23]

RFC 1894             Delivery Status Notifications          January 1996


    reverse-path ("<>") (so that no DSNs would be sent from a downstream
    MTA to the original sender),

(e) for messages forwarded to a confidential address, disabling delivery
    notifications for the forwarded message (e.g. if the "next-hop" MTA
    uses ESMTP and supports the DSN extension, by using the NOTIFY=NEVER
    parameter to the RCPT command), or

(f) when forwarding mail to a confidential address, having the
    forwarding MTA rewrite the envelope return address for the forwarded
    message and attempt delivery of that message as if the forwarding
    MTA were the originator.  On its receipt of final delivery status,
    the forwarding MTA would issue a DSN to the original sender.

   In general, any optional DSN field may be omitted if the Reporting
   MTA site determines that inclusion of the field would impose too
   great a compromise of site confidentiality.  The need for such
   confidentiality must be balanced against the utility of the omitted
   information in trouble reports and DSNs gatewayed to foreign
   environments.

   Implementors are cautioned that many existing MTAs will send
   nondelivery notifications to a return address in the message header
   (rather than to the one in the envelope), in violation of SMTP and
   other protocols.  If a message is forwarded through such an MTA, no
   reasonable action on the part of the forwarding MTA will prevent the
   downstream MTA from compromising the forwarding address.  Likewise,
   if the recipient's MTA automatically responds to messages based on a
   request in the message header (such as the nonstandard, but widely
   used, Return-Receipt-To extension header), it will also compromise
   the forwarding address.

4.3 Non-Repudiation

   Within the framework of today's internet mail, the DSNs defined in
   this memo provide valuable information to the mail user; however,
   even a "failed" DSN can not be relied upon as a guarantee that a
   message was not received by the recipient.  Even if DSNs are not
   actively forged, conditions exist under which a message can be
   delivered despite the fact that a failure DSN was issued.











Moore & Vaudreuil           Standards Track                    [Page 24]

RFC 1894             Delivery Status Notifications          January 1996


   For example, a race condition in the SMTP protocol allows for the
   duplication of messages if the connection is dropped following a
   completed DATA command, but before a response is seen by the SMTP
   client.  This will cause the SMTP client to retransmit the message,
   even though the SMTP server has already accepted it.[9] If one of
   those delivery attempts succeeds and the other one fails, a "failed"
   DSN could be issued even though the message actually reached the
   recipient.











































Moore & Vaudreuil           Standards Track                    [Page 25]

RFC 1894             Delivery Status Notifications          January 1996


5. Appendix - collected grammar

   NOTE:  The following lexical tokens are defined in RFC 822:  atom,
   CHAR, comment, CR, CRLF, DIGIT, LF, linear-white-space, SPACE, text.
   The date-time lexical token is defined in [8].

action-field = "Action" ":" action-value

action-value =
     "failed" / "delayed" / "delivered" / "relayed" / "expanded"

address-type = atom

arrival-date-field = "Arrival-Date" ":" date-time

delivery-status-content =
     per-message-fields 1*( CRLF per-recipient-fields )

diagnostic-code-field =
     "Diagnostic-Code" ":" diagnostic-type ";" *text

diagnostic-type = atom

dsn-gateway-field = "DSN-Gateway" ":" mta-name-type ";" mta-name

envelope-id = *text

extension-field = extension-field-name ":" *text

extension-field-name = atom

final-recipient-field =
     "Final-Recipient" ":" address-type ";" generic-address

generic-address = *text

last-attempt-date-field = "Last-Attempt-Date" ":" date-time

mta-name = *text

mta-name-type = atom

original-envelope-id-field =
     "Original-Envelope-Id" ":" envelope-id

original-recipient-field =
     "Original-Recipient" ":" address-type ";" generic-address




Moore & Vaudreuil           Standards Track                    [Page 26]

RFC 1894             Delivery Status Notifications          January 1996


per-message-fields =
     [ original-envelope-id-field CRLF ]
     reporting-mta-field CRLF
     [ dsn-gateway-field CRLF ]
     [ received-from-mta-field CRLF ]
     [ arrival-date-field CRLF ]
     *( extension-field CRLF )

per-recipient-fields =
     [ original-recipient-field CRLF ]
     final-recipient-field CRLF
     action-field CRLF
     status-field CRLF
     [ remote-mta-field CRLF ]
     [ diagnostic-code-field CRLF ]
     [ last-attempt-date-field CRLF ]
     [ will-retry-until-field CRLF ]
     *( extension-field CRLF )

received-from-mta-field =
     "Received-From-MTA" ":" mta-name-type ";" mta-name

remote-mta-field = "Remote-MTA" ":" mta-name-type ";" mta-name

reporting-mta-field =
     "Reporting-MTA" ":" mta-name-type ";" mta-name

status-code = DIGIT "." 1*3DIGIT "." 1*3DIGIT

     ; White-space characters and comments are NOT allowed within a
     ; status-code, though a comment enclosed in parentheses MAY follow
     ; the last numeric subfield of the status-code.  Each numeric
     ; subfield within the status-code MUST be expressed without
     ; leading zero digits.

status-field = "Status" ":" status-code

will-retry-until-field = "Will-Retry-Until" ":" date-time













Moore & Vaudreuil           Standards Track                    [Page 27]

RFC 1894             Delivery Status Notifications          January 1996


6. Appendix - Guidelines for gatewaying DSNs

   NOTE:  This section provides non-binding recommendations for the
   construction of mail gateways that wish to provide semi-transparent
   delivery reports between the Internet and another electronic mail
   system.  Specific DSN gateway requirements for a particular pair of
   mail systems may be defined by other documents.

6.1 Gatewaying from other mail systems to DSNs

   A mail gateway may issue a DSN to convey the contents of a "foreign"
   delivery or non-delivery notification over Internet mail.  When there
   are appropriate mappings from the foreign notification elements to
   DSN fields, the information may be transmitted in those DSN fields.
   Additional information (such as might be useful in a trouble ticket
   or needed to tunnel the foreign notification through the Internet)
   may be defined in extension DSN fields.  (Such fields should be given
   names that identify the foreign mail protocol, e.g. X400-* for X.400
   NDN or DN protocol elements)

   The gateway must attempt to supply reasonable values for the
   Reporting-MTA, Final-Recipient, Action, and Status fields.  These
   will normally be obtained by translating the values from the remote
   delivery or non-delivery notification into their Internet-style
   equivalents.  However, some loss of information is to be expected.
   For example, the set of status-codes defined for DSNs may not be
   adequate to fully convey the delivery diagnostic code from the
   foreign system.  The gateway should assign the most precise code
   which describes the failure condition, falling back on "generic"
   codes such as 2.0.0 (success), 4.0.0 (temporary failure), and 5.0.0
   (permanent failure) when necessary.  The actual foreign diagnostic
   code should be retained in the Diagnostic-Code field (with an
   appropriate diagnostic-type value) for use in trouble tickets or
   tunneling.

   The sender-specified recipient address, and the original envelope-id,
   if present in the foreign transport envelope, should be preserved in
   the Original-Recipient and Original-Envelope-ID fields.

   The gateway should also attempt to preserve the "final" recipient
   addresses and MTA names from the foreign system.  Whenever possible,
   foreign protocol elements should be encoded as meaningful printable
   ASCII strings.

   For DSNs produced from foreign delivery or nondelivery notifications,
   the name of the gateway MUST appear in the DSN-Gateway field of the
   DSN.




Moore & Vaudreuil           Standards Track                    [Page 28]

RFC 1894             Delivery Status Notifications          January 1996


6.2 Gatewaying from DSNs to other mail systems

   It may be possible to gateway DSNs from the Internet into a foreign
   mail system.  The primary purpose of such gatewaying is to convey
   delivery status information in a form that is usable by the
   destination system.  A secondary purpose is to allow "tunneling" of
   DSNs through foreign mail systems, in case the DSN may be gatewayed
   back into the Internet.

   In general, the recipient of the DSN (i.e., the sender of the
   original message) will want to know, for each recipient: the closest
   available approximation to the original recipient address, the
   delivery status (success, failure, or temporary failure), and for
   failed deliveries, a diagnostic code that describes the reason for
   the failure.

   If possible, the gateway should attempt to preserve the Original-
   Recipient address and Original-Envelope-ID (if present), in the
   resulting foreign delivery status report.

   When reporting delivery failures, if the diagnostic-type subfield of
   the Diagnostic-Code field indicates that the original diagnostic code
   is understood by the destination environment, the information from
   the Diagnostic-Code field should be used.  Failing that, the
   information in the Status field should be mapped into the closest
   available diagnostic code used in the destination environment.

   If it is possible to tunnel a DSN through the destination
   environment, the gateway specification may define a means of
   preserving the DSN information in the delivery status reports used by
   that environment.




















Moore & Vaudreuil           Standards Track                    [Page 29]

RFC 1894             Delivery Status Notifications          January 1996


7. Appendix - Guidelines for use of DSNs by mailing list exploders

   NOTE: This section pertains only to the use of DSNs by "mailing
   lists" as defined in [4], section 7.2.7.

   DSNs are designed to be used by mailing list exploders to allow them
   to detect and automatically delete recipients for whom mail delivery
   fails repeatedly.

   When forwarding a message to list subscribers, the mailing list
   exploder should always set the envelope return address (e.g. SMTP
   MAIL FROM address) to point to a special address which is set up to
   received nondelivery reports.  A "smart" mailing list exploder can
   therefore intercept such nondelivery reports, and if they are in the
   DSN format, automatically examine them to determine for which
   recipients a message delivery failed or was delayed.

   The Original-Recipient field should be used if available, since it
   should exactly match the subscriber address known to the list.  If
   the Original-Recipient field is not available, the recipient field
   may resemble the list subscriber address.  Often, however, the list
   subscriber will have forwarded his mail to a different address, or
   the address may be subject to some re-writing, so heuristics may be
   required to successfully match an address from the recipient field.
   Care is needed in this case to minimize the possibility of false
   matches.

   The reason for delivery failure can be obtained from the Status and
   Action fields, and from the Diagnostic-Code field (if the status-type
   is recognized).  Reports for recipients with action values other than
   "failed" can generally be ignored; in particular, subscribers should
   not be removed from a list due to "delayed" reports.

   In general, almost any failure status code (even a "permanent" one)
   can result from a temporary condition.  It is therefore recommended
   that a list exploder not delete a subscriber based on any single
   failure DSN (regardless of the status code), but only on the
   persistence of delivery failure over a period of time.

   However, some kinds of failures are less likely than others to have
   been caused by temporary conditions, and some kinds of failures are
   more likely to be noticed and corrected quickly than others.  Once
   more precise status codes are defined, it may be useful to
   differentiate between the status codes when deciding whether to
   delete a subscriber.  For example, on a list with a high message
   volume, it might be desirable to temporarily suspend delivery to a
   recipient address which causes repeated "temporary" failures, rather
   than simply deleting the recipient.  The duration of the suspension



Moore & Vaudreuil           Standards Track                    [Page 30]

RFC 1894             Delivery Status Notifications          January 1996


   might depend on the type of error.  On the other hand, a "user
   unknown" error which persisted for several days could be considered a
   reliable indication that address were no longer valid.

8. Appendix - IANA registration forms for DSN types

   The forms below are for use when registering a new address-type,
   diagnostic-type, or MTA-name-type with the Internet Assigned Numbers
   Authority (IANA).  Each piece of information requested by a
   registration form may be satisfied either by providing the
   information on the form itself, or by including a reference to a
   published, publicly available specification which includes the
   necessary information.  IANA MAY reject DSN type registrations
   because of incomplete registration forms, imprecise specifications,
   or inappropriate type names.

   To register a DSN type, complete the applicable form below and send
   it via Internet electronic mail to <IANA@IANA.ORG>.

8.1 IANA registration form for address-type

   A registration for a DSN address-type MUST include the following
   information:

(a) The proposed address-type name.

(b) The syntax for mailbox addresses of this type, specified using BNF,
    regular expressions, ASN.1, or other non-ambiguous language.

(c) If addresses of this type are not composed entirely of graphic
    characters from the US-ASCII repertoire, a specification for how
    they are to be encoded as graphic US-ASCII characters in a DSN
    Original-Recipient or Final-Recipient DSN field.

(d) [optional] A specification for how addresses of this type are to be
    translated to and from Internet electronic mail addresses.

8.2 IANA registration form for diagnostic-type

   A registration for a DSN address-type MUST include the following
   information:

(a) The proposed diagnostic-type name.

(b) A description of the syntax to be used for expressing diagnostic
    codes of this type as graphic characters from the US-ASCII
    repertoire.




Moore & Vaudreuil           Standards Track                    [Page 31]

RFC 1894             Delivery Status Notifications          January 1996


(c) A list of valid diagnostic codes of this type and the meaning of
    each code.

(d) [optional] A specification for mapping from diagnostic codes of this
    type to DSN status codes (as defined in [5]).

8.3 IANA registration form for MTA-name-type

   A registration for a DSN MTA-name-type must include the following
   information:

(a) The proposed MTA-name-type name.

(b) A description of the syntax of MTA names of this type, using BNF,
    regular expressions, ASN.1, or other non-ambiguous language.

(c) If MTA names of this type do not consist entirely of graphic
    characters from the US-ASCII repertoire, a specification for how an
    MTA name of this type should be expressed as a sequence of graphic
    US-ASCII characters.































Moore & Vaudreuil           Standards Track                    [Page 32]

RFC 1894             Delivery Status Notifications          January 1996


9. Appendix - Examples

   NOTE:  These examples are provided as illustration only, and are not
   considered part of the DSN protocol specification.  If an example
   conflicts with the protocol definition above, the example is wrong.

   Likewise, the use of *-type subfield names or extension fields in
   these examples is not to be construed as a definition for those type
   names or extension fields.

   These examples were manually translated from bounced messages using
   whatever information was available.







































Moore & Vaudreuil           Standards Track                    [Page 33]

RFC 1894             Delivery Status Notifications          January 1996


9.1  This is a simple DSN issued after repeated attempts
     to deliver a message failed.  In this case, the DSN is
     issued by the same MTA from which the message was originated.


   Date: Thu, 7 Jul 1994 17:16:05 -0400
   From: Mail Delivery Subsystem <MAILER-DAEMON@CS.UTK.EDU>
   Message-Id: <199407072116.RAA14128@CS.UTK.EDU>
   Subject: Returned mail: Cannot send message for 5 days
   To: <owner-info-mime@cs.utk.edu>
   MIME-Version: 1.0
   Content-Type: multipart/report; report-type=delivery-status;
         boundary="RAA14128.773615765/CS.UTK.EDU"

   --RAA14128.773615765/CS.UTK.EDU

   The original message was received at Sat, 2 Jul 1994 17:10:28 -0400
   from root@localhost

      ----- The following addresses had delivery problems -----
   <louisl@larry.slip.umd.edu>  (unrecoverable error)

      ----- Transcript of session follows -----
   <louisl@larry.slip.umd.edu>... Deferred: Connection timed out
         with larry.slip.umd.edu.
   Message could not be delivered for 5 days
   Message will be deleted from queue

   --RAA14128.773615765/CS.UTK.EDU
   content-type: message/delivery-status

   Reporting-MTA: dns; cs.utk.edu

   Original-Recipient: rfc822;louisl@larry.slip.umd.edu
   Final-Recipient: rfc822;louisl@larry.slip.umd.edu
   Action: failed
   Status: 4.0.0
   Diagnostic-Code: smtp; 426 connection timed out
   Last-Attempt-Date: Thu, 7 Jul 1994 17:15:49 -0400

   --RAA14128.773615765/CS.UTK.EDU
   content-type: message/rfc822

   [original message goes here]
   --RAA14128.773615765/CS.UTK.EDU--






Moore & Vaudreuil           Standards Track                    [Page 34]

RFC 1894             Delivery Status Notifications          January 1996


9.2  This is another DSN issued by the sender's MTA, which
     contains details of multiple delivery attempts.  Some of
     these were detected locally, and others by a remote MTA.


   Date: Fri, 8 Jul 1994 09:21:47 -0400
   From: Mail Delivery Subsystem <MAILER-DAEMON@CS.UTK.EDU>
   Subject: Returned mail: User unknown
   To: <owner-ups-mib@CS.UTK.EDU>
   MIME-Version: 1.0
   Content-Type: multipart/report; report-type=delivery-status;
         boundary="JAA13167.773673707/CS.UTK.EDU"

   --JAA13167.773673707/CS.UTK.EDU
   content-type: text/plain; charset=us-ascii

      ----- The following addresses had delivery problems -----
   <arathib@vnet.ibm.com>  (unrecoverable error)
   <wsnell@sdcc13.ucsd.edu>  (unrecoverable error)

   --JAA13167.773673707/CS.UTK.EDU
   content-type: message/delivery-status

   Reporting-MTA: dns; cs.utk.edu

   Original-Recipient: rfc822;arathib@vnet.ibm.com
   Final-Recipient: rfc822;arathib@vnet.ibm.com
   Action: failed
   Status: 5.0.0 (permanent failure)
   Diagnostic-Code: smtp;
    550 'arathib@vnet.IBM.COM' is not a registered gateway user
   Remote-MTA: dns; vnet.ibm.com

   Original-Recipient: rfc822;johnh@hpnjld.njd.hp.com
   Final-Recipient: rfc822;johnh@hpnjld.njd.hp.com
   Action: delayed
   Status: 4.0.0 (hpnjld.njd.jp.com: host name lookup failure)

   Original-Recipient: rfc822;wsnell@sdcc13.ucsd.edu
   Final-Recipient: rfc822;wsnell@sdcc13.ucsd.edu
   Action: failed
   Status: 5.0.0
   Diagnostic-Code: smtp; 550 user unknown
   Remote-MTA: dns; sdcc13.ucsd.edu

   --JAA13167.773673707/CS.UTK.EDU
   content-type: message/rfc822




Moore & Vaudreuil           Standards Track                    [Page 35]

RFC 1894             Delivery Status Notifications          January 1996


   [original message goes here]
   --JAA13167.773673707/CS.UTK.EDU--


9.3 A delivery report generated by Message Router (MAILBUS) and
    gatewayed by PMDF_MR to a DSN.  In this case the gateway did not
    have sufficient information to supply an original-recipient address.



   Disclose-recipients: prohibited
   Date: Fri, 08 Jul 1994 09:21:25 -0400 (EDT)
   From: Message Router Submission Agent <AMMGR@corp.timeplex.com>
   Subject: Status of : Re: Battery current sense
   To: owner-ups-mib@CS.UTK.EDU
   Message-id: <01HEGJ0WNBY28Y95LN@mr.timeplex.com>
   MIME-version: 1.0
   content-type: multipart/report; report-type=delivery-status;
         boundary="84229080704991.122306.SYS30"

   --84229080704991.122306.SYS30
   content-type: text/plain

   Invalid address - nair_s
   %DIR-E-NODIRMTCH, No matching Directory Entry found

   --84229080704991.122306.SYS30
   content-type: message/delivery-status

   Reporting-MTA: mailbus; SYS30

   Final-Recipient: unknown; nair_s
   Status: 5.0.0 (unknown permanent failure)
   Action: failed

   --84229080704991.122306.SYS30--















Moore & Vaudreuil           Standards Track                    [Page 36]

RFC 1894             Delivery Status Notifications          January 1996


9.4 A delay report from a multiprotocol MTA.  Note that there is no
    returned content, so no third body part appears in the DSN.

   From: <postmaster@nsfnet-relay.ac.uk>
   Message-Id: <199407092338.TAA23293@CS.UTK.EDU>
   Received: from nsfnet-relay.ac.uk by sun2.nsfnet-relay.ac.uk
             id <g.12954-0@sun2.nsfnet-relay.ac.uk>;
   Sun, 10 Jul 1994 00:36:51 +0100
   To: owner-info-mime@cs.utk.edu
   Date: Sun, 10 Jul 1994 00:36:51 +0100
   Subject: WARNING: message delayed at "nsfnet-relay.ac.uk"
   content-type: multipart/report; report-type=delivery-status;
         boundary=foobar

   --foobar
   content-type: text/plain

   The following message:

   UA-ID:  Reliable PC (...
   Q-ID:   sun2.nsf:77/msg.11820-0

   has not been delivered to the intended recipient:

   thomas@de-montfort.ac.uk

   despite repeated delivery attempts over the past 24 hours.

   The  usual cause of this problem is that the remote system is
   temporarily unavailable.

   Delivery will continue to be attempted up to a total elapsed
   time of  168 hours, ie 7 days.

   You  will  be  informed  if  delivery proves to be impossible
   within this time.

   Please quote the Q-ID in any queries regarding this mail.

   --foobar
   content-type: message/delivery-status

   Reporting-MTA: dns; sun2.nsfnet-relay.ac.uk

   Final-Recipient: rfc822;thomas@de-montfort.ac.uk
   Status: 4.0.0 (unknown temporary failure)
   Action: delayed




Moore & Vaudreuil           Standards Track                    [Page 37]

RFC 1894             Delivery Status Notifications          January 1996


   --foobar--

10. Acknowledgments

   The authors wish to thank the following people for their reviews of
   earlier drafts of this document and their suggestions for
   improvement:  Eric Allman, Harald Alvestrand, Allan Cargille, Jim
   Conklin, Peter Cowen, Dave Crocker, Roger Fajman, Ned Freed, Marko
   Kaittola, Steve Kille, John Klensin, John Gardiner Myers, Mark
   Nahabedian, Julian Onions, Jacob Palme, Jean Charles Roy, and Gregory
   Sheehan.

11. References

[1] Borenstein, N., Freed, N. "Multipurpose Internet Mail Extensions",
    RFC 1521, Bellcore, Innosoft, September 1993.

[2] Vaudreuil, G., "The Multipart/Report Content Type for the Reporting
    of Mail System Administrative Messages", RFC 1892, Octal Network
    Services, January 1996.

[3] Postel, J., "Simple Mail Transfer Protocol", STD 10, RFC 821,
    USC/Information Sciences Institute, August 1982.

[4] Moore, K., "SMTP Service Extension for Delivery Status
    Notifications", RFC 1891, University of Tennessee, January 1996.

[5] Vaudreuil, G., "Enhanced Mail System Status Codes", RFC 1893, Octal
    Network Services, January 1996.

[6] Crocker, D., "Standard for the Format of ARPA Internet Text
    Messages", STD 11, RFC 822, UDEL, August 1982.

[7] Moore, K. "MIME (Multipurpose Internet Mail Extensions) Part Two:
    Message Header Extensions for Non-Ascii Text", RFC 1522, University
    of Tennessee, September 1993.

[8] Braden, R. (ed.)  "Requirements for Internet Hosts - Application and
    Support", STD 3, RFC 1123, USC/Information Sciences Institute,
    October 1989.

[9] Partridge, C., "Duplicate Messages and SMTP", RFC 1047, BBN,
    February 1988.








Moore & Vaudreuil           Standards Track                    [Page 38]

RFC 1894             Delivery Status Notifications          January 1996


11. Authors' Addresses

   Keith Moore
   University of Tennessee
   107 Ayres Hall
   Knoxville, TN 37996-1301
   USA

   EMail: moore@cs.utk.edu
   Phone: +1 615 974 3126
   Fax: +1 615 974 8296


   Gregory M. Vaudreuil
   Octel Network Services
   17080 Dallas Parkway
   Dallas, TX 75248-1905
   USA

   EMail: Greg.Vaudreuil@Octel.Com































Moore & Vaudreuil           Standards Track                    [Page 39]