summaryrefslogtreecommitdiffstats
path: root/usr.sbin/sendmail/doc/rfc/rfc822.txt
blob: 35b09a3cb7eedde225d9aca27b9c8002c65927e3 (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
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
2188
2189
2190
2191
2192
2193
2194
2195
2196
2197
2198
2199
2200
2201
2202
2203
2204
2205
2206
2207
2208
2209
2210
2211
2212
2213
2214
2215
2216
2217
2218
2219
2220
2221
2222
2223
2224
2225
2226
2227
2228
2229
2230
2231
2232
2233
2234
2235
2236
2237
2238
2239
2240
2241
2242
2243
2244
2245
2246
2247
2248
2249
2250
2251
2252
2253
2254
2255
2256
2257
2258
2259
2260
2261
2262
2263
2264
2265
2266
2267
2268
2269
2270
2271
2272
2273
2274
2275
2276
2277
2278
2279
2280
2281
2282
2283
2284
2285
2286
2287
2288
2289
2290
2291
2292
2293
2294
2295
2296
2297
2298
2299
2300
2301
2302
2303
2304
2305
2306
2307
2308
2309
2310
2311
2312
2313
2314
2315
2316
2317
2318
2319
2320
2321
2322
2323
2324
2325
2326
2327
2328
2329
2330
2331
2332
2333
2334
2335
2336
2337
2338
2339
2340
2341
2342
2343
2344
2345
2346
2347
2348
2349
2350
2351
2352
2353
2354
2355
2356
2357
2358
2359
2360
2361
2362
2363
2364
2365
2366
2367
2368
2369
2370
2371
2372
2373
2374
2375
2376
2377
2378
2379
2380
2381
2382
2383
2384
2385
2386
2387
2388
2389
2390
2391
2392
2393
2394
2395
2396
2397
2398
2399
2400
2401
2402
2403
2404
2405
2406
2407
2408
2409
2410
2411
2412
2413
2414
2415
2416
2417
2418
2419
2420
2421
2422
2423
2424
2425
2426
2427
2428
2429
2430
2431
2432
2433
2434
2435
2436
2437
2438
2439
2440
2441
2442
2443
2444
2445
2446
2447
2448
2449
2450
2451
2452
2453
2454
2455
2456
2457
2458
2459
2460
2461
2462
2463
2464
2465
2466
2467
2468
2469
2470
2471
2472
2473
2474
2475
2476
2477
2478
2479
2480
2481
2482
2483
2484
2485
2486
2487
2488
2489
2490
2491
2492
2493
2494
2495
2496
2497
2498
2499
2500
2501
2502
2503
2504
2505
2506
2507
2508
2509
2510
2511
2512
2513
2514
2515
2516
2517
2518
2519
2520
2521
2522
2523
2524
2525
2526
2527
2528
2529
2530
2531
2532
2533
2534
2535
2536
2537
2538
2539
2540
2541
2542
2543
2544
2545
2546
2547
2548
2549
2550
2551
2552
2553
2554
2555
2556
2557
2558
2559
2560
2561
2562
2563
2564
2565
2566
2567
2568
2569
2570
2571
2572
2573
2574
2575
2576
2577
2578
2579
2580
2581
2582
2583
2584
2585
2586
2587
2588
2589
2590
2591
2592
2593
2594
2595
2596
2597
2598
2599
2600
2601
2602
2603
2604
2605
2606
2607
2608
2609
2610
2611
2612
2613
2614
2615
2616
2617
2618
2619
2620
2621
2622
2623
2624
2625
2626
2627
2628
2629
2630
2631
2632
2633
2634
2635
2636
2637
2638
2639
2640
2641
2642
2643
2644
2645
2646
2647
2648
2649
2650
2651
2652
2653
2654
2655
2656
2657
2658
2659
2660
2661
2662
2663
2664
2665
2666
2667
2668
2669
2670
2671
2672
2673
2674
2675
2676
2677
2678
2679
2680
2681
2682
2683
2684
2685
2686
2687
2688
2689
2690
2691
2692
2693
2694
2695
2696
2697
2698
2699
2700
2701
2702
2703
2704
2705
2706
2707
2708
2709
2710
2711
2712
2713
2714
2715
2716
2717
2718
2719
2720
2721
2722
2723
2724
2725
2726
2727
2728
2729
2730
2731
2732
2733
2734
2735
2736
2737
2738
2739
2740
2741
2742
2743
2744
2745
2746
2747
2748
2749
2750
2751
2752
2753
2754
2755
2756
2757
2758
2759
2760
2761
2762
2763
2764
2765
2766
2767
2768
2769
2770
2771
2772
2773
2774
2775
2776
2777
2778
2779
2780
2781
2782
2783
2784
2785
2786
2787
2788
2789
2790
2791
2792
2793
2794
2795
2796
2797
2798
2799
2800
2801
2802
2803
2804
2805
2806
2807
2808
2809
2810
2811
2812
2813
2814
2815
2816
2817
2818
2819
2820
2821
2822
2823
2824
2825
2826
2827
2828
2829
2830
2831
2832
2833
2834
2835
2836
2837
2838
2839
2840
2841
2842
2843
2844
2845
2846
2847
2848
2849
2850
2851
2852
2853
2854
2855
2856
2857
2858
2859
2860
2861
2862
2863
2864
2865
2866
2867
2868
2869
2870
2871
2872
2873
2874
2875
2876
2877
2878
2879
2880
2881
2882
2883
2884
2885
2886
2887
2888
2889
2890
2891
2892
2893
2894
2895
2896
2897
2898
2899
2900
2901

 




     RFC #  822

     Obsoletes:  RFC #733  (NIC #41952)












                        STANDARD FOR THE FORMAT OF

                        ARPA INTERNET TEXT MESSAGES






                              August 13, 1982






                                Revised by

                             David H. Crocker


                      Dept. of Electrical Engineering
                 University of Delaware, Newark, DE  19711
                      Network:  DCrocker @ UDel-Relay














 
     Standard for ARPA Internet Text Messages


                             TABLE OF CONTENTS


     PREFACE ....................................................   ii

     1.  INTRODUCTION ...........................................    1

         1.1.  Scope ............................................    1
         1.2.  Communication Framework ..........................    2

     2.  NOTATIONAL CONVENTIONS .................................    3

     3.  LEXICAL ANALYSIS OF MESSAGES ...........................    5

         3.1.  General Description ..............................    5
         3.2.  Header Field Definitions .........................    9
         3.3.  Lexical Tokens ...................................   10
         3.4.  Clarifications ...................................   11

     4.  MESSAGE SPECIFICATION ..................................   17

         4.1.  Syntax ...........................................   17
         4.2.  Forwarding .......................................   19
         4.3.  Trace Fields .....................................   20
         4.4.  Originator Fields ................................   21
         4.5.  Receiver Fields ..................................   23
         4.6.  Reference Fields .................................   23
         4.7.  Other Fields .....................................   24

     5.  DATE AND TIME SPECIFICATION ............................   26

         5.1.  Syntax ...........................................   26
         5.2.  Semantics ........................................   26

     6.  ADDRESS SPECIFICATION ..................................   27

         6.1.  Syntax ...........................................   27
         6.2.  Semantics ........................................   27
         6.3.  Reserved Address .................................   33

     7.  BIBLIOGRAPHY ...........................................   34


                             APPENDIX

     A.  EXAMPLES ...............................................   36
     B.  SIMPLE FIELD PARSING ...................................   40
     C.  DIFFERENCES FROM RFC #733 ..............................   41
     D.  ALPHABETICAL LISTING OF SYNTAX RULES ...................   44


     August 13, 1982               - i -                      RFC #822



 
     Standard for ARPA Internet Text Messages


                                  PREFACE


          By 1977, the Arpanet employed several informal standards for
     the  text  messages (mail) sent among its host computers.  It was
     felt necessary to codify these practices and  provide  for  those
     features  that  seemed  imminent.   The result of that effort was
     Request for Comments (RFC) #733, "Standard for the Format of ARPA
     Network Text Message", by Crocker, Vittal, Pogran, and Henderson.
     The specification attempted to avoid major  changes  in  existing
     software, while permitting several new features.

          This document revises the specifications  in  RFC  #733,  in
     order  to  serve  the  needs  of the larger and more complex ARPA
     Internet.  Some of RFC #733's features failed  to  gain  adequate
     acceptance.   In  order to simplify the standard and the software
     that follows it, these features have been removed.   A  different
     addressing  scheme  is  used, to handle the case of inter-network
     mail; and the concept of re-transmission has been introduced.

          This specification is intended for use in the ARPA Internet.
     However, an attempt has been made to free it of any dependence on
     that environment, so that it can be applied to other network text
     message systems.

          The specification of RFC #733 took place over the course  of
     one  year, using the ARPANET mail environment, itself, to provide
     an on-going forum for discussing the capabilities to be included.
     More  than  twenty individuals, from across the country, partici-
     pated in  the  original  discussion.   The  development  of  this
     revised specification has, similarly, utilized network mail-based
     group discussion.  Both specification efforts  greatly  benefited
     from the comments and ideas of the participants.

          The syntax of the standard,  in  RFC  #733,  was  originally
     specified  in  the  Backus-Naur Form (BNF) meta-language.  Ken L.
     Harrenstien, of SRI International, was responsible for  re-coding
     the  BNF  into  an  augmented  BNF  that makes the representation
     smaller and easier to understand.












     August 13, 1982              - ii -                      RFC #822


 
     Standard for ARPA Internet Text Messages


     1.  INTRODUCTION

     1.1.  SCOPE

          This standard specifies a syntax for text messages that  are
     sent  among  computer  users, within the framework of "electronic
     mail".  The standard supersedes  the  one  specified  in  ARPANET
     Request  for Comments #733, "Standard for the Format of ARPA Net-
     work Text Messages".

          In this context, messages are viewed as having  an  envelope
     and  contents.   The  envelope  contains  whatever information is
     needed to accomplish transmission  and  delivery.   The  contents
     compose  the object to be delivered to the recipient.  This stan-
     dard applies only to the format and some of the semantics of mes-
     sage  contents.   It contains no specification of the information
     in the envelope.

          However, some message systems may use information  from  the
     contents  to create the envelope.  It is intended that this stan-
     dard facilitate the acquisition of such information by programs.

          Some message systems may  store  messages  in  formats  that
     differ  from the one specified in this standard.  This specifica-
     tion is intended strictly as a definition of what message content
     format is to be passed BETWEEN hosts.

     Note:  This standard is NOT intended to dictate the internal for-
            mats  used  by sites, the specific message system features
            that they are expected to support, or any of  the  charac-
            teristics  of  user interface programs that create or read
            messages.

          A distinction should be made between what the  specification
     REQUIRES  and  what  it ALLOWS.  Messages can be made complex and
     rich with formally-structured components of information or can be
     kept small and simple, with a minimum of such information.  Also,
     the standard simplifies the interpretation  of  differing  visual
     formats  in  messages;  only  the  visual  aspect of a message is
     affected and not the interpretation  of  information  within  it.
     Implementors may choose to retain such visual distinctions.

          The formal definition is divided into four levels.  The bot-
     tom level describes the meta-notation used in this document.  The
     second level describes basic lexical analyzers that  feed  tokens
     to  higher-level  parsers.   Next is an overall specification for
     messages; it permits distinguishing individual fields.   Finally,
     there is definition of the contents of several structured fields.



     August 13, 1982               - 1 -                      RFC #822


 
     Standard for ARPA Internet Text Messages


     1.2.  COMMUNICATION FRAMEWORK

          Messages consist of lines of text.   No  special  provisions
     are  made for encoding drawings, facsimile, speech, or structured
     text.  No significant consideration has been given  to  questions
     of  data  compression  or to transmission and storage efficiency,
     and the standard tends to be free with the number  of  bits  con-
     sumed.   For  example,  field  names  are specified as free text,
     rather than special terse codes.

          A general "memo" framework is used.  That is, a message con-
     sists of some information in a rigid format, followed by the main
     part of the message, with a format that is not specified in  this
     document.   The  syntax of several fields of the rigidly-formated
     ("headers") section is defined in  this  specification;  some  of
     these fields must be included in all messages.

          The syntax  that  distinguishes  between  header  fields  is
     specified  separately  from  the  internal  syntax for particular
     fields.  This separation is intended to allow simple  parsers  to
     operate on the general structure of messages, without concern for
     the detailed structure of individual header fields.   Appendix  B
     is provided to facilitate construction of these parsers.

          In addition to the fields specified in this document, it  is
     expected  that  other fields will gain common use.  As necessary,
     the specifications for these "extension-fields" will be published
     through  the same mechanism used to publish this document.  Users
     may also  wish  to  extend  the  set  of  fields  that  they  use
     privately.  Such "user-defined fields" are permitted.

          The framework severely constrains document tone and  appear-
     ance and is primarily useful for most intra-organization communi-
     cations and  well-structured   inter-organization  communication.
     It  also  can  be used for some types of inter-process communica-
     tion, such as simple file transfer and remote job entry.  A  more
     robust  framework might allow for multi-font, multi-color, multi-
     dimension encoding of information.  A  less  robust  one,  as  is
     present  in  most  single-machine  message  systems,  would  more
     severely constrain the ability to add fields and the decision  to
     include specific fields.  In contrast with paper-based communica-
     tion, it is interesting to note that the RECEIVER  of  a  message
     can   exercise  an  extraordinary  amount  of  control  over  the
     message's appearance.  The amount of actual control available  to
     message  receivers  is  contingent upon the capabilities of their
     individual message systems.





     August 13, 1982               - 2 -                      RFC #822


 
     Standard for ARPA Internet Text Messages


     2.  NOTATIONAL CONVENTIONS

          This specification uses an augmented Backus-Naur Form  (BNF)
     notation.  The differences from standard BNF involve naming rules
     and indicating repetition and "local" alternatives.

     2.1.  RULE NAMING

          Angle brackets ("<", ">") are not  used,  in  general.   The
     name  of  a rule is simply the name itself, rather than "<name>".
     Quotation-marks enclose literal text (which may be  upper  and/or
     lower  case).   Certain  basic  rules  are  in uppercase, such as
     SPACE, TAB, CRLF, DIGIT, ALPHA, etc.  Angle brackets are used  in
     rule  definitions,  and  in  the rest of this  document, whenever
     their presence will facilitate discerning the use of rule names.

     2.2.  RULE1 / RULE2:  ALTERNATIVES

          Elements separated by slash ("/") are alternatives.   There-
     fore "foo / bar" will accept foo or bar.

     2.3.  (RULE1 RULE2):  LOCAL ALTERNATIVES

          Elements enclosed in parentheses are  treated  as  a  single
     element.   Thus,  "(elem  (foo  /  bar)  elem)"  allows the token
     sequences "elem foo elem" and "elem bar elem".

     2.4.  *RULE:  REPETITION

          The character "*" preceding an element indicates repetition.
     The full form is:

                              <l>*<m>element

     indicating at least <l> and at most <m> occurrences  of  element.
     Default values are 0 and infinity so that "*(element)" allows any
     number, including zero; "1*element" requires at  least  one;  and
     "1*2element" allows one or two.

     2.5.  [RULE]:  OPTIONAL

          Square brackets enclose optional elements; "[foo  bar]"   is
     equivalent to "*1(foo bar)".

     2.6.  NRULE:  SPECIFIC REPETITION

          "<n>(element)" is equivalent to "<n>*<n>(element)"; that is,
     exactly  <n>  occurrences  of (element). Thus 2DIGIT is a 2-digit
     number, and 3ALPHA is a string of three alphabetic characters.


     August 13, 1982               - 3 -                      RFC #822


 
     Standard for ARPA Internet Text Messages


     2.7.  #RULE:  LISTS

          A construct "#" is defined, similar to "*", as follows:

                              <l>#<m>element

     indicating at least <l> and at most <m> elements, each  separated
     by  one  or more commas (","). This makes the usual form of lists
     very easy; a rule such as '(element *("," element))' can be shown
     as  "1#element".   Wherever this construct is used, null elements
     are allowed, but do not  contribute  to  the  count  of  elements
     present.   That  is,  "(element),,(element)"  is  permitted,  but
     counts as only two elements.  Therefore, where at least one  ele-
     ment  is required, at least one non-null element must be present.
     Default values are 0 and infinity so that "#(element)" allows any
     number,  including  zero;  "1#element" requires at least one; and
     "1#2element" allows one or two.

     2.8.  ; COMMENTS

          A semi-colon, set off some distance to  the  right  of  rule
     text,  starts  a comment that continues to the end of line.  This
     is a simple way of including useful notes in  parallel  with  the
     specifications.



























     August 13, 1982               - 4 -                      RFC #822


 
     Standard for ARPA Internet Text Messages


     3.  LEXICAL ANALYSIS OF MESSAGES

     3.1.  GENERAL DESCRIPTION

          A message consists of header fields and, optionally, a body.
     The  body  is simply a sequence of lines containing ASCII charac-
     ters.  It is separated from the headers by a null line  (i.e.,  a
     line with nothing preceding the CRLF).

     3.1.1.  LONG HEADER FIELDS

        Each header field can be viewed as a single, logical  line  of
        ASCII  characters,  comprising  a field-name and a field-body.
        For convenience, the field-body  portion  of  this  conceptual
        entity  can be split into a multiple-line representation; this
        is called "folding".  The general rule is that wherever  there
        may  be  linear-white-space  (NOT  simply  LWSP-chars), a CRLF
        immediately followed by AT LEAST one LWSP-char may instead  be
        inserted.  Thus, the single line

            To:  "Joe & J. Harvey" <ddd @Org>, JJV @ BBN

        can be represented as:

            To:  "Joe & J. Harvey" <ddd @ Org>,
                    JJV@BBN

        and

            To:  "Joe & J. Harvey"
                            <ddd@ Org>, JJV
             @BBN

        and

            To:  "Joe &
             J. Harvey" <ddd @ Org>, JJV @ BBN

             The process of moving  from  this  folded   multiple-line
        representation  of a header field to its single line represen-
        tation is called "unfolding".  Unfolding  is  accomplished  by
        regarding   CRLF   immediately  followed  by  a  LWSP-char  as
        equivalent to the LWSP-char.

        Note:  While the standard  permits  folding  wherever  linear-
               white-space is permitted, it is recommended that struc-
               tured fields, such as those containing addresses, limit
               folding  to higher-level syntactic breaks.  For address
               fields, it  is  recommended  that  such  folding  occur


     August 13, 1982               - 5 -                      RFC #822


 
     Standard for ARPA Internet Text Messages


               between addresses, after the separating comma.

     3.1.2.  STRUCTURE OF HEADER FIELDS

        Once a field has been unfolded, it may be viewed as being com-
        posed of a field-name followed by a colon (":"), followed by a
        field-body, and  terminated  by  a  carriage-return/line-feed.
        The  field-name must be composed of printable ASCII characters
        (i.e., characters that  have  values  between  33.  and  126.,
        decimal, except colon).  The field-body may be composed of any
        ASCII characters, except CR or LF.  (While CR and/or LF may be
        present  in the actual text, they are removed by the action of
        unfolding the field.)

        Certain field-bodies of headers may be  interpreted  according
        to  an  internal  syntax  that some systems may wish to parse.
        These  fields  are  called  "structured   fields".    Examples
        include  fields containing dates and addresses.  Other fields,
        such as "Subject"  and  "Comments",  are  regarded  simply  as
        strings of text.

        Note:  Any field which has a field-body  that  is  defined  as
               other  than  simply <text> is to be treated as a struc-
               tured field.

               Field-names, unstructured field bodies  and  structured
               field bodies each are scanned by their own, independent
               "lexical" analyzers.

     3.1.3.  UNSTRUCTURED FIELD BODIES

        For some fields, such as "Subject" and "Comments",  no  struc-
        turing  is assumed, and they are treated simply as <text>s, as
        in the message body.  Rules of folding apply to these  fields,
        so  that  such  field  bodies  which occupy several lines must
        therefore have the second and successive lines indented by  at
        least one LWSP-char.

     3.1.4.  STRUCTURED FIELD BODIES

        To aid in the creation and reading of structured  fields,  the
        free  insertion   of linear-white-space (which permits folding
        by inclusion of CRLFs)  is  allowed  between  lexical  tokens.
        Rather  than  obscuring  the  syntax  specifications for these
        structured fields with explicit syntax for this  linear-white-
        space, the existence of another "lexical" analyzer is assumed.
        This analyzer does not apply  for  unstructured  field  bodies
        that  are  simply  strings  of  text, as described above.  The
        analyzer provides  an  interpretation  of  the  unfolded  text


     August 13, 1982               - 6 -                      RFC #822


 
     Standard for ARPA Internet Text Messages


        composing  the body of the field as a sequence of lexical sym-
        bols.

        These symbols are:

                     -  individual special characters
                     -  quoted-strings
                     -  domain-literals
                     -  comments
                     -  atoms

        The first four of these symbols  are  self-delimiting.   Atoms
        are not; they are delimited by the self-delimiting symbols and
        by  linear-white-space.   For  the  purposes  of  regenerating
        sequences  of  atoms  and quoted-strings, exactly one SPACE is
        assumed to exist, and should be used, between them.  (Also, in
        the "Clarifications" section on "White Space", below, note the
        rules about treatment of multiple contiguous LWSP-chars.)

        So, for example, the folded body of an address field

            ":sysmail"@  Some-Group. Some-Org,
            Muhammed.(I am  the greatest) Ali @(the)Vegas.WBA




























     August 13, 1982               - 7 -                      RFC #822


 
     Standard for ARPA Internet Text Messages


        is analyzed into the following lexical symbols and types:

                    :sysmail              quoted string
                    @                     special
                    Some-Group            atom
                    .                     special
                    Some-Org              atom
                    ,                     special
                    Muhammed              atom
                    .                     special
                    (I am  the greatest)  comment
                    Ali                   atom
                    @                     atom
                    (the)                 comment
                    Vegas                 atom
                    .                     special
                    WBA                   atom

        The canonical representations for the data in these  addresses
        are the following strings:

                        ":sysmail"@Some-Group.Some-Org

        and

                            Muhammed.Ali@Vegas.WBA

        Note:  For purposes of display, and when passing  such  struc-
               tured information to other systems, such as mail proto-
               col  services,  there  must  be  NO  linear-white-space
               between  <word>s  that are separated by period (".") or
               at-sign ("@") and exactly one SPACE between  all  other
               <word>s.  Also, headers should be in a folded form.


















     August 13, 1982               - 8 -                      RFC #822


 
     Standard for ARPA Internet Text Messages


     3.2.  HEADER FIELD DEFINITIONS

          These rules show a field meta-syntax, without regard for the
     particular  type  or internal syntax.  Their purpose is to permit
     detection of fields; also, they present to  higher-level  parsers
     an image of each field as fitting on one line.

     field       =  field-name ":" [ field-body ] CRLF

     field-name  =  1*<any CHAR, excluding CTLs, SPACE, and ":">

     field-body  =  field-body-contents
                    [CRLF LWSP-char field-body]

     field-body-contents =
                   <the ASCII characters making up the field-body, as
                    defined in the following sections, and consisting
                    of combinations of atom, quoted-string, and
                    specials tokens, or else consisting of texts>
































     August 13, 1982               - 9 -                      RFC #822


 
     Standard for ARPA Internet Text Messages


     3.3.  LEXICAL TOKENS

          The following rules are used to define an underlying lexical
     analyzer,  which  feeds  tokens to higher level parsers.  See the
     ANSI references, in the Bibliography.

                                                 ; (  Octal, Decimal.)
     CHAR        =  <any ASCII character>        ; (  0-177,  0.-127.)
     ALPHA       =  <any ASCII alphabetic character>
                                                 ; (101-132, 65.- 90.)
                                                 ; (141-172, 97.-122.)
     DIGIT       =  <any ASCII decimal digit>    ; ( 60- 71, 48.- 57.)
     CTL         =  <any ASCII control           ; (  0- 37,  0.- 31.)
                     character and DEL>          ; (    177,     127.)
     CR          =  <ASCII CR, carriage return>  ; (     15,      13.)
     LF          =  <ASCII LF, linefeed>         ; (     12,      10.)
     SPACE       =  <ASCII SP, space>            ; (     40,      32.)
     HTAB        =  <ASCII HT, horizontal-tab>   ; (     11,       9.)
     <">         =  <ASCII quote mark>           ; (     42,      34.)
     CRLF        =  CR LF

     LWSP-char   =  SPACE / HTAB                 ; semantics = SPACE

     linear-white-space =  1*([CRLF] LWSP-char)  ; semantics = SPACE
                                                 ; CRLF => folding

     specials    =  "(" / ")" / "<" / ">" / "@"  ; Must be in quoted-
                 /  "," / ";" / ":" / "\" / <">  ;  string, to use
                 /  "." / "[" / "]"              ;  within a word.

     delimiters  =  specials / linear-white-space / comment

     text        =  <any CHAR, including bare    ; => atoms, specials,
                     CR & bare LF, but NOT       ;  comments and
                     including CRLF>             ;  quoted-strings are
                                                 ;  NOT recognized.

     atom        =  1*<any CHAR except specials, SPACE and CTLs>

     quoted-string = <"> *(qtext/quoted-pair) <">; Regular qtext or
                                                 ;   quoted chars.

     qtext       =  <any CHAR excepting <">,     ; => may be folded
                     "\" & CR, and including
                     linear-white-space>

     domain-literal =  "[" *(dtext / quoted-pair) "]"




     August 13, 1982              - 10 -                      RFC #822


 
     Standard for ARPA Internet Text Messages


     dtext       =  <any CHAR excluding "[",     ; => may be folded
                     "]", "\" & CR, & including
                     linear-white-space>

     comment     =  "(" *(ctext / quoted-pair / comment) ")"

     ctext       =  <any CHAR excluding "(",     ; => may be folded
                     ")", "\" & CR, & including
                     linear-white-space>

     quoted-pair =  "\" CHAR                     ; may quote any char

     phrase      =  1*word                       ; Sequence of words

     word        =  atom / quoted-string


     3.4.  CLARIFICATIONS

     3.4.1.  QUOTING

        Some characters are reserved for special interpretation,  such
        as  delimiting lexical tokens.  To permit use of these charac-
        ters as uninterpreted data, a quoting mechanism  is  provided.
        To quote a character, precede it with a backslash ("\").

        This mechanism is not fully general.  Characters may be quoted
        only  within  a subset of the lexical constructs.  In particu-
        lar, quoting is limited to use within:

                             -  quoted-string
                             -  domain-literal
                             -  comment

        Within these constructs, quoting is REQUIRED for  CR  and  "\"
        and for the character(s) that delimit the token (e.g., "(" and
        ")" for a comment).  However, quoting  is  PERMITTED  for  any
        character.

        Note:  In particular, quoting is NOT permitted  within  atoms.
               For  example  when  the local-part of an addr-spec must
               contain a special character, a quoted  string  must  be
               used.  Therefore, a specification such as:

                            Full\ Name@Domain

               is not legal and must be specified as:

                            "Full Name"@Domain


     August 13, 1982              - 11 -                      RFC #822


 
     Standard for ARPA Internet Text Messages


     3.4.2.  WHITE SPACE

        Note:  In structured field bodies, multiple linear space ASCII
               characters  (namely  HTABs  and  SPACEs) are treated as
               single spaces and may freely surround any  symbol.   In
               all header fields, the only place in which at least one
               LWSP-char is REQUIRED is at the beginning of  continua-
               tion lines in a folded field.

        When passing text to processes  that  do  not  interpret  text
        according to this standard (e.g., mail protocol servers), then
        NO linear-white-space characters should occur between a period
        (".") or at-sign ("@") and a <word>.  Exactly ONE SPACE should
        be used in place of arbitrary linear-white-space  and  comment
        sequences.

        Note:  Within systems conforming to this standard, wherever  a
               member of the list of delimiters is allowed, LWSP-chars
               may also occur before and/or after it.

        Writers of  mail-sending  (i.e.,  header-generating)  programs
        should realize that there is no network-wide definition of the
        effect of ASCII HT (horizontal-tab) characters on the  appear-
        ance  of  text  at another network host; therefore, the use of
        tabs in message headers, though permitted, is discouraged.

     3.4.3.  COMMENTS

        A comment is a set of ASCII characters, which is  enclosed  in
        matching  parentheses  and which is not within a quoted-string
        The comment construct permits message originators to add  text
        which  will  be  useful  for  human readers, but which will be
        ignored by the formal semantics.  Comments should be  retained
        while  the  message  is subject to interpretation according to
        this standard.  However, comments  must  NOT  be  included  in
        other  cases,  such  as  during  protocol  exchanges with mail
        servers.

        Comments nest, so that if an unquoted left parenthesis  occurs
        in  a  comment  string,  there  must  also be a matching right
        parenthesis.  When a comment acts as the delimiter  between  a
        sequence of two lexical symbols, such as two atoms, it is lex-
        ically equivalent with a single SPACE,  for  the  purposes  of
        regenerating  the  sequence, such as when passing the sequence
        onto a mail protocol server.  Comments are  detected  as  such
        only within field-bodies of structured fields.

        If a comment is to be "folded" onto multiple lines,  then  the
        syntax  for  folding  must  be  adhered to.  (See the "Lexical


     August 13, 1982              - 12 -                      RFC #822


 
     Standard for ARPA Internet Text Messages


        Analysis of Messages" section on "Folding Long Header  Fields"
        above,  and  the  section on "Case Independence" below.)  Note
        that  the  official  semantics  therefore  do  not  "see"  any
        unquoted CRLFs that are in comments, although particular pars-
        ing programs may wish to note their presence.  For these  pro-
        grams,  it would be reasonable to interpret a "CRLF LWSP-char"
        as being a CRLF that is part of the comment; i.e., the CRLF is
        kept  and  the  LWSP-char is discarded.  Quoted CRLFs (i.e., a
        backslash followed by a CR followed by a  LF)  still  must  be
        followed by at least one LWSP-char.

     3.4.4.  DELIMITING AND QUOTING CHARACTERS

        The quote character (backslash) and  characters  that  delimit
        syntactic  units  are not, generally, to be taken as data that
        are part of the delimited or quoted unit(s).   In  particular,
        the   quotation-marks   that   define   a  quoted-string,  the
        parentheses that define  a  comment  and  the  backslash  that
        quotes  a  following  character  are  NOT  part of the quoted-
        string, comment or quoted character.  A quotation-mark that is
        to  be  part  of  a quoted-string, a parenthesis that is to be
        part of a comment and a backslash that is to be part of either
        must  each be preceded by the quote-character backslash ("\").
        Note that the syntax allows any character to be quoted  within
        a  quoted-string  or  comment; however only certain characters
        MUST be quoted to be included as data.  These  characters  are
        the  ones that are not part of the alternate text group (i.e.,
        ctext or qtext).

        The one exception to this rule  is  that  a  single  SPACE  is
        assumed  to  exist  between  contiguous words in a phrase, and
        this interpretation is independent of  the  actual  number  of
        LWSP-chars  that  the  creator  places  between the words.  To
        include more than one SPACE, the creator must make  the  LWSP-
        chars be part of a quoted-string.

        Quotation marks that delimit a quoted string  and  backslashes
        that  quote  the  following character should NOT accompany the
        quoted-string when the string is passed to processes  that  do
        not interpret data according to this specification (e.g., mail
        protocol servers).

     3.4.5.  QUOTED-STRINGS

        Where permitted (i.e., in words in structured fields)  quoted-
        strings  are  treated  as a single symbol.  That is, a quoted-
        string is equivalent to an atom, syntactically.  If a  quoted-
        string  is to be "folded" onto multiple lines, then the syntax
        for folding must be adhered to.  (See the "Lexical Analysis of


     August 13, 1982              - 13 -                      RFC #822


 
     Standard for ARPA Internet Text Messages


        Messages"  section  on "Folding Long Header Fields" above, and
        the section on "Case  Independence"  below.)   Therefore,  the
        official  semantics  do  not  "see" any bare CRLFs that are in
        quoted-strings; however particular parsing programs  may  wish
        to  note  their presence.  For such programs, it would be rea-
        sonable to interpret a "CRLF LWSP-char" as being a CRLF  which
        is  part  of the quoted-string; i.e., the CRLF is kept and the
        LWSP-char is discarded.  Quoted CRLFs (i.e., a backslash  fol-
        lowed  by  a CR followed by a LF) are also subject to rules of
        folding, but the presence of the quoting character (backslash)
        explicitly  indicates  that  the  CRLF  is  data to the quoted
        string.  Stripping off the first following LWSP-char  is  also
        appropriate when parsing quoted CRLFs.

     3.4.6.  BRACKETING CHARACTERS

        There is one type of bracket which must occur in matched pairs
        and may have pairs nested within each other:

            o   Parentheses ("(" and ")") are used  to  indicate  com-
                ments.

        There are three types of brackets which must occur in  matched
        pairs, and which may NOT be nested:

            o   Colon/semi-colon (":" and ";") are   used  in  address
                specifications  to  indicate that the included list of
                addresses are to be treated as a group.

            o   Angle brackets ("<" and ">")  are  generally  used  to
                indicate  the  presence of a one machine-usable refer-
                ence (e.g., delimiting mailboxes), possibly  including
                source-routing to the machine.

            o   Square brackets ("[" and "]") are used to indicate the
                presence  of  a  domain-literal, which the appropriate
                name-domain  is  to  use  directly,  bypassing  normal
                name-resolution mechanisms.

     3.4.7.  CASE INDEPENDENCE

        Except as noted, alphabetic strings may be represented in  any
        combination of upper and lower case.  The only syntactic units








     August 13, 1982              - 14 -                      RFC #822


 
     Standard for ARPA Internet Text Messages


        which requires preservation of case information are:

                    -  text
                    -  qtext
                    -  dtext
                    -  ctext
                    -  quoted-pair
                    -  local-part, except "Postmaster"

        When matching any other syntactic unit, case is to be ignored.
        For  example, the field-names "From", "FROM", "from", and even
        "FroM" are semantically equal and should all be treated ident-
        ically.

        When generating these units, any mix of upper and  lower  case
        alphabetic  characters  may  be  used.  The case shown in this
        specification is suggested for message-creating processes.

        Note:  The reserved local-part address unit, "Postmaster",  is
               an  exception.   When  the  value "Postmaster" is being
               interpreted, it must be  accepted  in  any  mixture  of
               case, including "POSTMASTER", and "postmaster".

     3.4.8.  FOLDING LONG HEADER FIELDS

        Each header field may be represented on exactly one line  con-
        sisting  of the name of the field and its body, and terminated
        by a CRLF; this is what the parser sees.  For readability, the
        field-body  portion of long header fields may be "folded" onto
        multiple lines of the actual field.  "Long" is commonly inter-
        preted  to  mean greater than 65 or 72 characters.  The former
        length serves as a limit, when the message is to be viewed  on
        most  simple terminals which use simple display software; how-
        ever, the limit is not imposed by this standard.

        Note:  Some display software often can selectively fold lines,
               to  suit  the display terminal.  In such cases, sender-
               provided  folding  can  interfere  with   the   display
               software.

     3.4.9.  BACKSPACE CHARACTERS

        ASCII BS characters (Backspace, decimal 8) may be included  in
        texts and quoted-strings to effect overstriking.  However, any
        use of backspaces which effects an overstrike to the  left  of
        the beginning of the text or quoted-string is prohibited.





     August 13, 1982              - 15 -                      RFC #822


 
     Standard for ARPA Internet Text Messages


     3.4.10.  NETWORK-SPECIFIC TRANSFORMATIONS

        During transmission through heterogeneous networks, it may  be
        necessary  to  force data to conform to a network's local con-
        ventions.  For example, it may be required that a CR  be  fol-
        lowed  either by LF, making a CRLF, or by <null>, if the CR is
        to stand alone).  Such transformations are reversed, when  the
        message exits that network.

        When  crossing  network  boundaries,  the  message  should  be
        treated  as  passing  through  two modules.  It will enter the
        first module containing whatever network-specific  transforma-
        tions  that  were  necessary  to  permit migration through the
        "current" network.  It then passes through the modules:

            o   Transformation Reversal

                The "current" network's idiosyncracies are removed and
                the  message  is returned to the canonical form speci-
                fied in this standard.

            o   Transformation

                The "next" network's local idiosyncracies are  imposed
                on the message.

                                ------------------
                    From   ==>  | Remove Net-A   |
                    Net-A       | idiosyncracies |
                                ------------------
                                       ||
                                       \/
                                  Conformance
                                  with standard
                                       ||
                                       \/
                                ------------------
                                | Impose Net-B   |  ==>  To
                                | idiosyncracies |       Net-B
                                ------------------











     August 13, 1982              - 16 -                      RFC #822


 
     Standard for ARPA Internet Text Messages


     4.  MESSAGE SPECIFICATION

     4.1.  SYNTAX

     Note:  Due to an artifact of the notational conventions, the syn-
            tax  indicates that, when present, some fields, must be in
            a particular order.  Header fields  are  NOT  required  to
            occur  in  any  particular  order, except that the message
            body must occur AFTER  the  headers.   It  is  recommended
            that,  if  present,  headers be sent in the order "Return-
            Path", "Received", "Date",  "From",  "Subject",  "Sender",
            "To", "cc", etc.

            This specification permits multiple  occurrences  of  most
            fields.   Except  as  noted,  their  interpretation is not
            specified here, and their use is discouraged.

          The following syntax for the bodies of various fields should
     be  thought  of  as  describing  each field body as a single long
     string (or line).  The "Lexical Analysis of Message"  section  on
     "Long  Header Fields", above, indicates how such long strings can
     be represented on more than one line in  the  actual  transmitted
     message.

     message     =  fields *( CRLF *text )       ; Everything after
                                                 ;  first null line
                                                 ;  is message body

     fields      =    dates                      ; Creation time,
                      source                     ;  author id & one
                    1*destination                ;  address required
                     *optional-field             ;  others optional

     source      = [  trace ]                    ; net traversals
                      originator                 ; original mail
                   [  resent ]                   ; forwarded

     trace       =    return                     ; path to sender
                    1*received                   ; receipt tags

     return      =  "Return-path" ":" route-addr ; return address

     received    =  "Received"    ":"            ; one per relay
                       ["from" domain]           ; sending host
                       ["by"   domain]           ; receiving host
                       ["via"  atom]             ; physical path
                      *("with" atom)             ; link/mail protocol
                       ["id"   msg-id]           ; receiver msg id
                       ["for"  addr-spec]        ; initial form


     August 13, 1982              - 17 -                      RFC #822


 
     Standard for ARPA Internet Text Messages


                        ";"    date-time         ; time received

     originator  =   authentic                   ; authenticated addr
                   [ "Reply-To"   ":" 1#address] )

     authentic   =   "From"       ":"   mailbox  ; Single author
                 / ( "Sender"     ":"   mailbox  ; Actual submittor
                     "From"       ":" 1#mailbox) ; Multiple authors
                                                 ;  or not sender

     resent      =   resent-authentic
                   [ "Resent-Reply-To"  ":" 1#address] )

     resent-authentic =
                 =   "Resent-From"      ":"   mailbox
                 / ( "Resent-Sender"    ":"   mailbox
                     "Resent-From"      ":" 1#mailbox  )

     dates       =   orig-date                   ; Original
                   [ resent-date ]               ; Forwarded

     orig-date   =  "Date"        ":"   date-time

     resent-date =  "Resent-Date" ":"   date-time

     destination =  "To"          ":" 1#address  ; Primary
                 /  "Resent-To"   ":" 1#address
                 /  "cc"          ":" 1#address  ; Secondary
                 /  "Resent-cc"   ":" 1#address
                 /  "bcc"         ":"  #address  ; Blind carbon
                 /  "Resent-bcc"  ":"  #address

     optional-field =
                 /  "Message-ID"        ":"   msg-id
                 /  "Resent-Message-ID" ":"   msg-id
                 /  "In-Reply-To"       ":"  *(phrase / msg-id)
                 /  "References"        ":"  *(phrase / msg-id)
                 /  "Keywords"          ":"  #phrase
                 /  "Subject"           ":"  *text
                 /  "Comments"          ":"  *text
                 /  "Encrypted"         ":" 1#2word
                 /  extension-field              ; To be defined
                 /  user-defined-field           ; May be pre-empted

     msg-id      =  "<" addr-spec ">"            ; Unique message id






     August 13, 1982              - 18 -                      RFC #822


 
     Standard for ARPA Internet Text Messages


     extension-field =
                   <Any field which is defined in a document
                    published as a formal extension to this
                    specification; none will have names beginning
                    with the string "X-">

     user-defined-field =
                   <Any field which has not been defined
                    in this specification or published as an
                    extension to this specification; names for
                    such fields must be unique and may be
                    pre-empted by published extensions>

     4.2.  FORWARDING

          Some systems permit mail recipients to  forward  a  message,
     retaining  the original headers, by adding some new fields.  This
     standard supports such a service, through the "Resent-" prefix to
     field names.

          Whenever the string "Resent-" begins a field name, the field
     has  the  same  semantics as a field whose name does not have the
     prefix.  However, the message is assumed to have  been  forwarded
     by  an original recipient who attached the "Resent-" field.  This
     new field is treated as being more recent  than  the  equivalent,
     original  field.   For  example, the "Resent-From", indicates the
     person that forwarded the message, whereas the "From" field indi-
     cates the original author.

          Use of such precedence  information  depends  upon  partici-
     pants'  communication needs.  For example, this standard does not
     dictate when a "Resent-From:" address should receive replies,  in
     lieu of sending them to the "From:" address.

     Note:  In general, the "Resent-" fields should be treated as con-
            taining  a  set  of information that is independent of the
            set of original fields.  Information for  one  set  should
            not  automatically be taken from the other.  The interpre-
            tation of multiple "Resent-" fields, of the same type,  is
            undefined.

          In the remainder of this specification, occurrence of  legal
     "Resent-"  fields  are treated identically with the occurrence of








     August 13, 1982              - 19 -                      RFC #822


 
     Standard for ARPA Internet Text Messages


     fields whose names do not contain this prefix.

     4.3.  TRACE FIELDS

          Trace information is used to provide an audit trail of  mes-
     sage  handling.   In  addition,  it indicates a route back to the
     sender of the message.

          The list of known "via" and  "with"  values  are  registered
     with  the  Network  Information  Center, SRI International, Menlo
     Park, California.

     4.3.1.  RETURN-PATH

        This field  is  added  by  the  final  transport  system  that
        delivers  the message to its recipient.  The field is intended
        to contain definitive information about the address and  route
        back to the message's originator.

        Note:  The "Reply-To" field is added  by  the  originator  and
               serves  to  direct  replies,  whereas the "Return-Path"
               field is used to identify a path back to  the  origina-
               tor.

        While the syntax  indicates  that  a  route  specification  is
        optional,  every attempt should be made to provide that infor-
        mation in this field.

     4.3.2.  RECEIVED

        A copy of this field is added by each transport  service  that
        relays the message.  The information in the field can be quite
        useful for tracing transport problems.

        The names of the sending  and  receiving  hosts  and  time-of-
        receipt may be specified.  The "via" parameter may be used, to
        indicate what physical mechanism the message  was  sent  over,
        such  as  Arpanet or Phonenet, and the "with" parameter may be
        used to indicate the mail-,  or  connection-,  level  protocol
        that  was  used, such as the SMTP mail protocol, or X.25 tran-
        sport protocol.

        Note:  Several "with" parameters may  be  included,  to  fully
               specify the set of protocols that were used.

        Some transport services queue mail; the internal message iden-
        tifier that is assigned to the message may be noted, using the
        "id" parameter.  When the  sending  host  uses  a  destination
        address specification that the receiving host reinterprets, by


     August 13, 1982              - 20 -                      RFC #822


 
     Standard for ARPA Internet Text Messages


        expansion or transformation, the receiving host  may  wish  to
        record  the original specification, using the "for" parameter.
        For example, when a copy of mail is sent to the  member  of  a
        distribution  list,  this  parameter may be used to record the
        original address that was used to specify the list.

     4.4.  ORIGINATOR FIELDS

          The standard allows only a subset of the combinations possi-
     ble  with the From, Sender, Reply-To, Resent-From, Resent-Sender,
     and Resent-Reply-To fields.  The limitation is intentional.

     4.4.1.  FROM / RESENT-FROM

        This field contains the identity of the person(s)  who  wished
        this  message to be sent.  The message-creation process should
        default this field  to  be  a  single,  authenticated  machine
        address,  indicating  the  AGENT  (person,  system or process)
        entering the message.  If this is not done, the "Sender" field
        MUST  be  present.  If the "From" field IS defaulted this way,
        the "Sender" field is  optional  and  is  redundant  with  the
        "From"  field.   In  all  cases, addresses in the "From" field
        must be machine-usable (addr-specs) and may not contain  named
        lists (groups).

     4.4.2.  SENDER / RESENT-SENDER

        This field contains the authenticated identity  of  the  AGENT
        (person,  system  or  process)  that sends the message.  It is
        intended for use when the sender is not the author of the mes-
        sage,  or  to  indicate  who among a group of authors actually
        sent the message.  If the contents of the "Sender" field would
        be  completely  redundant  with  the  "From"  field,  then the
        "Sender" field need not be present and its use is  discouraged
        (though  still legal).  In particular, the "Sender" field MUST
        be present if it is NOT the same as the "From" Field.

        The Sender mailbox  specification  includes  a  word  sequence
        which  must correspond to a specific agent (i.e., a human user
        or a computer program) rather than a standard  address.   This
        indicates  the  expectation  that  the field will identify the
        single AGENT (person,  system,  or  process)  responsible  for
        sending  the mail and not simply include the name of a mailbox
        from which the mail was sent.  For example in the  case  of  a
        shared login name, the name, by itself, would not be adequate.
        The local-part address unit, which refers to  this  agent,  is
        expected to be a computer system term, and not (for example) a
        generalized person reference which can  be  used  outside  the
        network text message context.


     August 13, 1982              - 21 -                      RFC #822


 
     Standard for ARPA Internet Text Messages


        Since the critical function served by the  "Sender"  field  is
        identification  of  the agent responsible for sending mail and
        since computer programs cannot be held accountable  for  their
        behavior, it is strongly recommended that when a computer pro-
        gram generates a message, the HUMAN  who  is  responsible  for
        that program be referenced as part of the "Sender" field mail-
        box specification.

     4.4.3.  REPLY-TO / RESENT-REPLY-TO

        This field provides a general  mechanism  for  indicating  any
        mailbox(es)  to which responses are to be sent.  Three typical
        uses for this feature can  be  distinguished.   In  the  first
        case,  the  author(s) may not have regular machine-based mail-
        boxes and therefore wish(es) to indicate an alternate  machine
        address.   In  the  second case, an author may wish additional
        persons to be made aware of, or responsible for,  replies.   A
        somewhat  different  use  may be of some help to "text message
        teleconferencing" groups equipped with automatic  distribution
        services:   include the address of that service in the "Reply-
        To" field of all messages  submitted  to  the  teleconference;
        then  participants  can  "reply"  to conference submissions to
        guarantee the correct distribution of any submission of  their
        own.

        Note:  The "Return-Path" field is added by the mail  transport
               service,  at the time of final deliver.  It is intended
               to identify a path back to the orginator  of  the  mes-
               sage.   The  "Reply-To"  field  is added by the message
               originator and is intended to direct replies.

     4.4.4.  AUTOMATIC USE OF FROM / SENDER / REPLY-TO

        For systems which automatically  generate  address  lists  for
        replies to messages, the following recommendations are made:

            o   The "Sender" field mailbox should be sent  notices  of
                any  problems in transport or delivery of the original
                messages.  If there is no  "Sender"  field,  then  the
                "From" field mailbox should be used.

            o   The  "Sender"  field  mailbox  should  NEVER  be  used
                automatically, in a recipient's reply message.

            o   If the "Reply-To" field exists, then the reply  should
                go to the addresses indicated in that field and not to
                the address(es) indicated in the "From" field.




     August 13, 1982              - 22 -                      RFC #822


 
     Standard for ARPA Internet Text Messages


            o   If there is a "From" field, but no  "Reply-To"  field,
                the  reply should be sent to the address(es) indicated
                in the "From" field.

        Sometimes, a recipient may actually wish to  communicate  with
        the  person  that  initiated  the  message  transfer.  In such
        cases, it is reasonable to use the "Sender" address.

        This recommendation is intended  only  for  automated  use  of
        originator-fields  and is not intended to suggest that replies
        may not also be sent to other recipients of messages.   It  is
        up  to  the  respective  mail-handling programs to decide what
        additional facilities will be provided.

        Examples are provided in Appendix A.

     4.5.  RECEIVER FIELDS

     4.5.1.  TO / RESENT-TO

        This field contains the identity of the primary recipients  of
        the message.

     4.5.2.  CC / RESENT-CC

        This field contains the identity of  the  secondary  (informa-
        tional) recipients of the message.

     4.5.3.  BCC / RESENT-BCC

        This field contains the identity of additional  recipients  of
        the  message.   The contents of this field are not included in
        copies of the message sent to the primary and secondary  reci-
        pients.   Some  systems  may choose to include the text of the
        "Bcc" field only in the author(s)'s  copy,  while  others  may
        also include it in the text sent to all those indicated in the
        "Bcc" list.

     4.6.  REFERENCE FIELDS

     4.6.1.  MESSAGE-ID / RESENT-MESSAGE-ID

             This field contains a unique identifier  (the  local-part
        address  unit)  which  refers to THIS version of THIS message.
        The uniqueness of the message identifier is guaranteed by  the
        host  which  generates  it.  This identifier is intended to be
        machine readable and not necessarily meaningful to humans.   A
        message  identifier pertains to exactly one instantiation of a
        particular message; subsequent revisions to the message should


     August 13, 1982              - 23 -                      RFC #822


 
     Standard for ARPA Internet Text Messages


        each receive new message identifiers.

     4.6.2.  IN-REPLY-TO

             The contents of this field identify  previous  correspon-
        dence  which this message answers.  Note that if message iden-
        tifiers are used in this  field,  they  must  use  the  msg-id
        specification format.

     4.6.3.  REFERENCES

             The contents of this field identify other  correspondence
        which  this message references.  Note that if message identif-
        iers are used, they must use the msg-id specification format.

     4.6.4.  KEYWORDS

             This field contains keywords  or  phrases,  separated  by
        commas.

     4.7.  OTHER FIELDS

     4.7.1.  SUBJECT

             This is intended to provide a summary,  or  indicate  the
        nature, of the message.

     4.7.2.  COMMENTS

             Permits adding text comments  onto  the  message  without
        disturbing the contents of the message's body.

     4.7.3.  ENCRYPTED

             Sometimes,  data  encryption  is  used  to  increase  the
        privacy  of  message  contents.   If the body of a message has
        been encrypted, to keep its contents private, the  "Encrypted"
        field  can be used to note the fact and to indicate the nature
        of the encryption.  The first <word> parameter  indicates  the
        software  used  to  encrypt the body, and the second, optional
        <word> is intended to  aid  the  recipient  in  selecting  the
        proper  decryption  key.   This  code word may be viewed as an
        index to a table of keys held by the recipient.

        Note:  Unfortunately, headers must contain envelope,  as  well
               as  contents,  information.  Consequently, it is neces-
               sary that they remain unencrypted, so that  mail  tran-
               sport   services   may   access   them.   Since  names,
               addresses, and "Subject"  field  contents  may  contain


     August 13, 1982              - 24 -                      RFC #822


 
     Standard for ARPA Internet Text Messages


               sensitive  information,  this  requirement limits total
               message privacy.

             Names of encryption software are registered with the Net-
        work  Information Center, SRI International, Menlo Park, Cali-
        fornia.

     4.7.4.  EXTENSION-FIELD

             A limited number of common fields have  been  defined  in
        this  document.   As  network mail requirements dictate, addi-
        tional fields may be standardized.   To  provide  user-defined
        fields  with  a  measure  of  safety,  in name selection, such
        extension-fields will never have names  that  begin  with  the
        string "X-".

             Names of Extension-fields are registered with the Network
        Information Center, SRI International, Menlo Park, California.

     4.7.5.  USER-DEFINED-FIELD

             Individual users of network mail are free to  define  and
        use  additional  header  fields.   Such fields must have names
        which are not already used in the current specification or  in
        any definitions of extension-fields, and the overall syntax of
        these user-defined-fields must conform to this specification's
        rules   for   delimiting  and  folding  fields.   Due  to  the
        extension-field  publishing  process,  the  name  of  a  user-
        defined-field may be pre-empted

        Note:  The prefatory string "X-" will never  be  used  in  the
               names  of Extension-fields.  This provides user-defined
               fields with a protected set of names.


















     August 13, 1982              - 25 -                      RFC #822


 
     Standard for ARPA Internet Text Messages


     5.  DATE AND TIME SPECIFICATION

     5.1.  SYNTAX

     date-time   =  [ day "," ] date time        ; dd mm yy
                                                 ;  hh:mm:ss zzz

     day         =  "Mon"  / "Tue" /  "Wed"  / "Thu"
                 /  "Fri"  / "Sat" /  "Sun"

     date        =  1*2DIGIT month 2DIGIT        ; day month year
                                                 ;  e.g. 20 Jun 82

     month       =  "Jan"  /  "Feb" /  "Mar"  /  "Apr"
                 /  "May"  /  "Jun" /  "Jul"  /  "Aug"
                 /  "Sep"  /  "Oct" /  "Nov"  /  "Dec"

     time        =  hour zone                    ; ANSI and Military

     hour        =  2DIGIT ":" 2DIGIT [":" 2DIGIT]
                                                 ; 00:00:00 - 23:59:59

     zone        =  "UT"  / "GMT"                ; Universal Time
                                                 ; North American : UT
                 /  "EST" / "EDT"                ;  Eastern:  - 5/ - 4
                 /  "CST" / "CDT"                ;  Central:  - 6/ - 5
                 /  "MST" / "MDT"                ;  Mountain: - 7/ - 6
                 /  "PST" / "PDT"                ;  Pacific:  - 8/ - 7
                 /  1ALPHA                       ; Military: Z = UT;
                                                 ;  A:-1; (J not used)
                                                 ;  M:-12; N:+1; Y:+12
                 / ( ("+" / "-") 4DIGIT )        ; Local differential
                                                 ;  hours+min. (HHMM)

     5.2.  SEMANTICS

          If included, day-of-week must be the day implied by the date
     specification.

          Time zone may be indicated in several ways.  "UT" is Univer-
     sal  Time  (formerly called "Greenwich Mean Time"); "GMT" is per-
     mitted as a reference to Universal Time.  The  military  standard
     uses  a  single  character for each zone.  "Z" is Universal Time.
     "A" indicates one hour earlier, and "M" indicates 12  hours  ear-
     lier;  "N"  is  one  hour  later, and "Y" is 12 hours later.  The
     letter "J" is not used.  The other remaining two forms are  taken
     from ANSI standard X3.51-1975.  One allows explicit indication of
     the amount of offset from UT; the other uses  common  3-character
     strings for indicating time zones in North America.


     August 13, 1982              - 26 -                      RFC #822


 
     Standard for ARPA Internet Text Messages


     6.  ADDRESS SPECIFICATION

     6.1.  SYNTAX

     address     =  mailbox                      ; one addressee
                 /  group                        ; named list

     group       =  phrase ":" [#mailbox] ";"

     mailbox     =  addr-spec                    ; simple address
                 /  phrase route-addr            ; name & addr-spec

     route-addr  =  "<" [route] addr-spec ">"

     route       =  1#("@" domain) ":"           ; path-relative

     addr-spec   =  local-part "@" domain        ; global address

     local-part  =  word *("." word)             ; uninterpreted
                                                 ; case-preserved

     domain      =  sub-domain *("." sub-domain)

     sub-domain  =  domain-ref / domain-literal

     domain-ref  =  atom                         ; symbolic reference

     6.2.  SEMANTICS

          A mailbox receives mail.  It is a  conceptual  entity  which
     does  not necessarily pertain to file storage.  For example, some
     sites may choose to print mail on their line printer and  deliver
     the output to the addressee's desk.

          A mailbox specification comprises a person, system  or  pro-
     cess name reference, a domain-dependent string, and a name-domain
     reference.  The name reference is optional and is usually used to
     indicate  the  human name of a recipient.  The name-domain refer-
     ence specifies a sequence of sub-domains.   The  domain-dependent
     string is uninterpreted, except by the final sub-domain; the rest
     of the mail service merely transmits it as a literal string.

     6.2.1.  DOMAINS

        A name-domain is a set of registered (mail)  names.   A  name-
        domain  specification  resolves  to  a subordinate name-domain
        specification  or  to  a  terminal  domain-dependent   string.
        Hence,  domain  specification  is  extensible,  permitting any
        number of registration levels.


     August 13, 1982              - 27 -                      RFC #822


 
     Standard for ARPA Internet Text Messages


        Name-domains model a global, logical, hierarchical  addressing
        scheme.   The  model is logical, in that an address specifica-
        tion is related to name registration and  is  not  necessarily
        tied  to  transmission  path.   The  model's  hierarchy  is  a
        directed graph, called an in-tree, such that there is a single
        path  from  the root of the tree to any node in the hierarchy.
        If more than one path actually exists, they are considered  to
        be different addresses.

        The root node is common to all addresses; consequently, it  is
        not  referenced.   Its  children  constitute "top-level" name-
        domains.  Usually, a service has access to its own full domain
        specification and to the names of all top-level name-domains.

        The "top" of the domain addressing hierarchy -- a child of the
        root  --  is  indicated  by  the right-most field, in a domain
        specification.  Its child is specified to the left, its  child
        to the left, and so on.

        Some groups provide formal registration services;  these  con-
        stitute   name-domains   that  are  independent  logically  of
        specific machines.  In addition, networks and machines  impli-
        citly  compose name-domains, since their membership usually is
        registered in name tables.

        In the case of formal registration, an organization implements
        a  (distributed)  data base which provides an address-to-route
        mapping service for addresses of the form:

                         person@registry.organization

        Note that "organization" is a logical  entity,  separate  from
        any particular communication network.

        A mechanism for accessing "organization" is universally avail-
        able.   That mechanism, in turn, seeks an instantiation of the
        registry; its location is not indicated in the address specif-
        ication.   It  is assumed that the system which operates under
        the name "organization" knows how to find a subordinate regis-
        try.  The registry will then use the "person" string to deter-
        mine where to send the mail specification.

        The latter,  network-oriented  case  permits  simple,  direct,
        attachment-related address specification, such as:

                              user@host.network

        Once the network is accessed, it is expected  that  a  message
        will  go  directly  to the host and that the host will resolve


     August 13, 1982              - 28 -                      RFC #822


 
     Standard for ARPA Internet Text Messages


        the user name, placing the message in the user's mailbox.

     6.2.2.  ABBREVIATED DOMAIN SPECIFICATION

        Since any number of  levels  is  possible  within  the  domain
        hierarchy,  specification  of  a  fully  qualified address can
        become inconvenient.  This standard permits abbreviated domain
        specification, in a special case:

            For the address of  the  sender,  call  the  left-most
            sub-domain  Level  N.   In a header address, if all of
            the sub-domains above (i.e., to the right of) Level  N
            are  the same as those of the sender, then they do not
            have to appear in the specification.   Otherwise,  the
            address must be fully qualified.

            This feature is subject  to  approval  by  local  sub-
            domains.   Individual  sub-domains  may  require their
            member systems, which originate mail, to provide  full
            domain  specification only.  When permitted, abbrevia-
            tions may be present  only  while  the  message  stays
            within the sub-domain of the sender.

            Use of this mechanism requires the sender's sub-domain
            to reserve the names of all top-level domains, so that
            full specifications can be distinguished from abbrevi-
            ated specifications.

        For example, if a sender's address is:

                 sender@registry-A.registry-1.organization-X

        and one recipient's address is:

                recipient@registry-B.registry-1.organization-X

        and another's is:

                recipient@registry-C.registry-2.organization-X

        then ".registry-1.organization-X" need not be specified in the
        the  message,  but  "registry-C.registry-2"  DOES  have  to be
        specified.  That is, the first two addresses may  be  abbrevi-
        ated, but the third address must be fully specified.

        When a message crosses a domain boundary, all  addresses  must
        be  specified  in  the  full format, ending with the top-level
        name-domain in the right-most field.  It is the responsibility
        of  mail  forwarding services to ensure that addresses conform


     August 13, 1982              - 29 -                      RFC #822


 
     Standard for ARPA Internet Text Messages


        with this requirement.  In the case of abbreviated  addresses,
        the  relaying  service must make the necessary expansions.  It
        should be noted that it often is difficult for such a  service
        to locate all occurrences of address abbreviations.  For exam-
        ple, it will not be possible to find such abbreviations within
        the  body  of  the  message.   The "Return-Path" field can aid
        recipients in recovering from these errors.

        Note:  When passing any portion of an addr-spec onto a process
               which  does  not interpret data according to this stan-
               dard (e.g., mail protocol servers).  There must  be  NO
               LWSP-chars  preceding  or  following the at-sign or any
               delimiting period ("."), such as  shown  in  the  above
               examples,   and   only  ONE  SPACE  between  contiguous
               <word>s.

     6.2.3.  DOMAIN TERMS

        A domain-ref must be THE official name of a registry, network,
        or  host.   It  is  a  symbolic  reference, within a name sub-
        domain.  At times, it is necessary to bypass standard  mechan-
        isms  for  resolving  such  references,  using  more primitive
        information, such as a network host address  rather  than  its
        associated host name.

        To permit such references, this standard provides the  domain-
        literal  construct.   Its contents must conform with the needs
        of the sub-domain in which it is interpreted.

        Domain-literals which refer to domains within the ARPA  Inter-
        net  specify  32-bit  Internet addresses, in four 8-bit fields
        noted in decimal, as described in Request for  Comments  #820,
        "Assigned Numbers."  For example:

                                 [10.0.3.19]

        Note:  THE USE OF DOMAIN-LITERALS IS STRONGLY DISCOURAGED.  It
               is  permitted  only  as  a means of bypassing temporary
               system limitations, such as name tables which  are  not
               complete.

        The names of "top-level" domains, and  the  names  of  domains
        under  in  the  ARPA Internet, are registered with the Network
        Information Center, SRI International, Menlo Park, California.

     6.2.4.  DOMAIN-DEPENDENT LOCAL STRING

        The local-part of an  addr-spec  in  a  mailbox  specification
        (i.e.,  the  host's  name for the mailbox) is understood to be


     August 13, 1982              - 30 -                      RFC #822


 
     Standard for ARPA Internet Text Messages


        whatever the receiving mail protocol server allows.  For exam-
        ple,  some systems do not understand mailbox references of the
        form "P. D. Q. Bach", but others do.

        This specification treats periods (".") as lexical separators.
        Hence,  their  presence  in  local-parts which are not quoted-
        strings, is detected.   However,  such  occurrences  carry  NO
        semantics.  That is, if a local-part has periods within it, an
        address parser will divide the local-part into several tokens,
        but  the  sequence  of  tokens will be treated as one uninter-
        preted unit.  The sequence  will  be  re-assembled,  when  the
        address is passed outside of the system such as to a mail pro-
        tocol service.

        For example, the address:

                           First.Last@Registry.Org

        is legal and does not require the local-part to be  surrounded
        with  quotation-marks.   (However,  "First  Last" DOES require
        quoting.)  The local-part of the address, when passed  outside
        of  the  mail  system,  within  the  Registry.Org  domain,  is
        "First.Last", again without quotation marks.

     6.2.5.  BALANCING LOCAL-PART AND DOMAIN

        In some cases, the boundary between local-part and domain  can
        be  flexible.  The local-part may be a simple string, which is
        used for the final determination of the  recipient's  mailbox.
        All  other  levels  of  reference  are, therefore, part of the
        domain.

        For some systems, in the case of abbreviated reference to  the
        local  and  subordinate  sub-domains,  it  may  be possible to
        specify only one reference within the domain  part  and  place
        the  other,  subordinate  name-domain  references  within  the
        local-part.  This would appear as:

                        mailbox.sub1.sub2@this-domain

        Such a specification would be acceptable  to  address  parsers
        which  conform  to  RFC  #733,  but  do not support this newer
        Internet standard.  While contrary to the intent of this stan-
        dard, the form is legal.

        Also, some sub-domains have a specification syntax which  does
        not conform to this standard.  For example:

                      sub-net.mailbox@sub-domain.domain


     August 13, 1982              - 31 -                      RFC #822


 
     Standard for ARPA Internet Text Messages


        uses a different parsing  sequence  for  local-part  than  for
        domain.

        Note:  As a rule,  the  domain  specification  should  contain
               fields  which  are  encoded  according to the syntax of
               this standard and which contain  generally-standardized
               information.   The local-part specification should con-
               tain only that portion of the  address  which  deviates
               from the form or intention of the domain field.

     6.2.6.  MULTIPLE MAILBOXES

        An individual may have several mailboxes and wish  to  receive
        mail  at  whatever  mailbox  is  convenient  for the sender to
        access.  This standard does not provide a means of  specifying
        "any member of" a list of mailboxes.

        A set of individuals may wish to receive mail as a single unit
        (i.e.,  a  distribution  list).  The <group> construct permits
        specification of such a list.  Recipient mailboxes are  speci-
        fied  within  the  bracketed  part (":" - ";").  A copy of the
        transmitted message is to be  sent  to  each  mailbox  listed.
        This  standard  does  not  permit  recursive  specification of
        groups within groups.

        While a list must be named, it is not required that  the  con-
        tents  of  the  list be included.  In this case, the <address>
        serves only as an indication of group distribution  and  would
        appear in the form:

                                    name:;

        Some mail  services  may  provide  a  group-list  distribution
        facility,  accepting  a single mailbox reference, expanding it
        to the full distribution list, and relaying the  mail  to  the
        list's  members.   This standard provides no additional syntax
        for indicating such a  service.   Using  the  <group>  address
        alternative,  while listing one mailbox in it, can mean either
        that the mailbox reference will be expanded to a list or  that
        there is a group with one member.

     6.2.7.  EXPLICIT PATH SPECIFICATION

        At times, a  message  originator  may  wish  to  indicate  the
        transmission  path  that  a  message  should  follow.  This is
        called source routing.  The normal addressing scheme, used  in
        an  addr-spec,  is  carefully separated from such information;
        the <route> portion of a route-addr is provided for such occa-
        sions.  It specifies the sequence of hosts and/or transmission


     August 13, 1982              - 32 -                      RFC #822


 
     Standard for ARPA Internet Text Messages


        services that are  to  be  traversed.   Both  domain-refs  and
        domain-literals may be used.

        Note:  The use of source routing is discouraged.   Unless  the
               sender has special need of path restriction, the choice
               of transmission route should be left to the mail  tran-
               sport service.

     6.3.  RESERVED ADDRESS

          It often is necessary to send mail to a site, without  know-
     ing  any  of its valid addresses.  For example, there may be mail
     system dysfunctions, or a user may wish to find  out  a  person's
     correct address, at that site.

          This standard specifies a single, reserved  mailbox  address
     (local-part)  which  is  to  be valid at each site.  Mail sent to
     that address is to be routed to  a  person  responsible  for  the
     site's mail system or to a person with responsibility for general
     site operation.  The name of the reserved local-part address is:

                                Postmaster

     so that "Postmaster@domain" is required to be valid.

     Note:  This reserved local-part must be  matched  without  sensi-
            tivity to alphabetic case, so that "POSTMASTER", "postmas-
            ter", and even "poStmASteR" is to be accepted.























     August 13, 1982              - 33 -                      RFC #822


 
     Standard for ARPA Internet Text Messages


     7.  BIBLIOGRAPHY


     ANSI.  "USA Standard Code  for  Information  Interchange,"  X3.4.
        American  National Standards Institute: New York (1968).  Also
        in:  Feinler, E.  and J. Postel, eds., "ARPANET Protocol Hand-
        book", NIC 7104.

     ANSI.  "Representations of Universal Time, Local  Time  Differen-
        tials,  and United States Time Zone References for Information
        Interchange," X3.51-1975.  American National Standards  Insti-
        tute:  New York (1975).

     Bemer, R.W., "Time and the Computer."  In:  Interface  Age  (Feb.
        1979).

     Bennett, C.J.  "JNT Mail Protocol".  Joint Network Team,  Ruther-
        ford and Appleton Laboratory:  Didcot, England.

     Bhushan, A.K., Pogran, K.T., Tomlinson,  R.S.,  and  White,  J.E.
        "Standardizing  Network  Mail  Headers,"   ARPANET Request for
        Comments No. 561, Network Information Center  No.  18516;  SRI
        International:  Menlo Park (September 1973).

     Birrell, A.D., Levin, R.,  Needham,  R.M.,  and  Schroeder,  M.D.
        "Grapevine:  An Exercise in Distributed Computing," Communica-
        tions of the ACM 25, 4 (April 1982), 260-274.

     Crocker,  D.H.,  Vittal,  J.J.,  Pogran,  K.T.,  Henderson,  D.A.
        "Standard  for  the  Format  of  ARPA  Network  Text Message,"
        ARPANET Request for  Comments  No.  733,  Network  Information
        Center  No.  41952.   SRI International:  Menlo Park (November
        1977).

     Feinler, E.J. and Postel, J.B.  ARPANET Protocol  Handbook,  Net-
        work  Information  Center  No.  7104   (NTIS AD A003890).  SRI
        International:  Menlo Park (April 1976).

     Harary, F.   "Graph  Theory".   Addison-Wesley:   Reading,  Mass.
        (1969).

     Levin, R. and Schroeder, M.  "Transport  of  Electronic  Messages
        through  a  Network,"   TeleInformatics  79, pp. 29-33.  North
        Holland (1979).  Also  as  Xerox  Palo  Alto  Research  Center
        Technical Report CSL-79-4.

     Myer, T.H. and Henderson, D.A.  "Message Transmission  Protocol,"
        ARPANET  Request  for  Comments,  No. 680, Network Information
        Center No. 32116.  SRI International:  Menlo Park (1975).


     August 13, 1982              - 34 -                      RFC #822


 
     Standard for ARPA Internet Text Messages


     NBS.  "Specification of Message Format for Computer Based Message
        Systems, Recommended Federal Information Processing Standard."
        National  Bureau   of   Standards:    Gaithersburg,   Maryland
        (October 1981).

     NIC.  Internet Protocol Transition Workbook.  Network Information
        Center,   SRI-International,  Menlo  Park,  California  (March
        1982).

     Oppen, D.C. and Dalal, Y.K.  "The Clearinghouse:  A Decentralized
        Agent  for  Locating  Named  Objects in a Distributed Environ-
        ment," OPD-T8103.  Xerox Office Products Division:  Palo Alto,
        CA. (October 1981).

     Postel, J.B.  "Assigned Numbers,"  ARPANET Request for  Comments,
        No. 820.  SRI International:  Menlo Park (August 1982).

     Postel, J.B.  "Simple Mail Transfer  Protocol,"  ARPANET  Request
        for Comments, No. 821.  SRI International:  Menlo Park (August
        1982).

     Shoch, J.F.  "Internetwork naming, addressing  and  routing,"  in
        Proc. 17th IEEE Computer Society International Conference, pp.
        72-79, Sept. 1978, IEEE Cat. No. 78 CH 1388-8C.

     Su, Z. and Postel, J.  "The Domain Naming Convention for Internet
        User  Applications,"  ARPANET  Request  for Comments, No. 819.
        SRI International:  Menlo Park (August 1982).























     August 13, 1982              - 35 -                      RFC #822


 
     Standard for ARPA Internet Text Messages


                                 APPENDIX


     A.  EXAMPLES

     A.1.  ADDRESSES

     A.1.1.  Alfred Neuman <Neuman@BBN-TENEXA>

     A.1.2.  Neuman@BBN-TENEXA

             These two "Alfred Neuman" examples have identical  seman-
        tics, as far as the operation of the local host's mail sending
        (distribution) program (also sometimes  called  its  "mailer")
        and  the remote host's mail protocol server are concerned.  In
        the first example, the  "Alfred  Neuman"  is  ignored  by  the
        mailer,  as "Neuman@BBN-TENEXA" completely specifies the reci-
        pient.  The second example contains  no  superfluous  informa-
        tion,  and,  again,  "Neuman@BBN-TENEXA" is the intended reci-
        pient.

        Note:  When the message crosses name-domain  boundaries,  then
               these specifications must be changed, so as to indicate
               the remainder of the hierarchy, starting with  the  top
               level.

     A.1.3.  "George, Ted" <Shared@Group.Arpanet>

             This form might be used to indicate that a single mailbox
        is  shared  by several users.  The quoted string is ignored by
        the originating host's mailer, because  "Shared@Group.Arpanet"
        completely specifies the destination mailbox.

     A.1.4.  Wilt . (the  Stilt) Chamberlain@NBA.US

             The "(the  Stilt)" is a comment, which is NOT included in
        the  destination  mailbox  address  handed  to the originating
        system's mailer.  The local-part of the address is the  string
        "Wilt.Chamberlain", with NO space between the first and second
        words.

     A.1.5.  Address Lists

     Gourmets:  Pompous Person <WhoZiWhatZit@Cordon-Bleu>,
                Childs@WGBH.Boston, Galloping Gourmet@
                ANT.Down-Under (Australian National Television),
                Cheapie@Discount-Liquors;,
       Cruisers:  Port@Portugal, Jones@SEA;,
         Another@Somewhere.SomeOrg


     August 13, 1982              - 36 -                      RFC #822


 
     Standard for ARPA Internet Text Messages


        This group list example points out the use of comments and the
        mixing of addresses and groups.

     A.2.  ORIGINATOR ITEMS

     A.2.1.  Author-sent

             George Jones logs into his host  as  "Jones".   He  sends
        mail himself.

            From:  Jones@Group.Org

        or

            From:  George Jones <Jones@Group.Org>

     A.2.2.  Secretary-sent

             George Jones logs in as Jones on his  host.   His  secre-
        tary,  who logs in as Secy sends mail for him.  Replies to the
        mail should go to George.

            From:    George Jones <Jones@Group>
            Sender:  Secy@Other-Group

     A.2.3.  Secretary-sent, for user of shared directory

             George Jones' secretary sends mail  for  George.  Replies
        should go to George.

            From:     George Jones<Shared@Group.Org>
            Sender:   Secy@Other-Group

        Note that there need not be a space between  "Jones"  and  the
        "<",  but  adding a space enhances readability (as is the case
        in other examples.

     A.2.4.  Committee activity, with one author

             George is a member of a committee.  He wishes to have any
        replies to his message go to all committee members.

            From:     George Jones <Jones@Host.Net>
            Sender:   Jones@Host
            Reply-To: The Committee: Jones@Host.Net,
                                     Smith@Other.Org,
                                     Doe@Somewhere-Else;

        Note  that  if  George  had  not  included  himself   in   the


     August 13, 1982              - 37 -                      RFC #822


 
     Standard for ARPA Internet Text Messages


        enumeration  of  The  Committee,  he  would not have gotten an
        implicit reply; the presence of the  "Reply-to"  field  SUPER-
        SEDES the sending of a reply to the person named in the "From"
        field.

     A.2.5.  Secretary acting as full agent of author

             George Jones asks his secretary  (Secy@Host)  to  send  a
        message for him in his capacity as Group.  He wants his secre-
        tary to handle all replies.

            From:     George Jones <Group@Host>
            Sender:   Secy@Host
            Reply-To: Secy@Host

     A.2.6.  Agent for user without online mailbox

             A friend  of  George's,  Sarah,  is  visiting.   George's
        secretary  sends  some  mail to a friend of Sarah in computer-
        land.  Replies should go to George, whose mailbox is Jones  at
        Registry.

            From:     Sarah Friendly <Secy@Registry>
            Sender:   Secy-Name <Secy@Registry>
            Reply-To: Jones@Registry.

     A.2.7.  Agent for member of a committee

             George's secretary sends out a message which was authored
        jointly by all the members of a committee.  Note that the name
        of the committee cannot be specified, since <group> names  are
        not permitted in the From field.

            From:   Jones@Host,
                    Smith@Other-Host,
                    Doe@Somewhere-Else
            Sender: Secy@SHost














     August 13, 1982              - 38 -                      RFC #822


 
     Standard for ARPA Internet Text Messages


     A.3.  COMPLETE HEADERS

     A.3.1.  Minimum required

     Date:     26 Aug 76 1429 EDT        Date:     26 Aug 76 1429 EDT
     From:     Jones@Registry.Org   or   From:     Jones@Registry.Org
     Bcc:                                To:       Smith@Registry.Org

        Note that the "Bcc" field may be empty, while the  "To"  field
        is required to have at least one address.

     A.3.2.  Using some of the additional fields

     Date:     26 Aug 76 1430 EDT
     From:     George Jones<Group@Host>
     Sender:   Secy@SHOST
     To:       "Al Neuman"@Mad-Host,
               Sam.Irving@Other-Host
     Message-ID:  <some.string@SHOST>

     A.3.3.  About as complex as you're going to get

     Date     :  27 Aug 76 0932 PDT
     From     :  Ken Davis <KDavis@This-Host.This-net>
     Subject  :  Re: The Syntax in the RFC
     Sender   :  KSecy@Other-Host
     Reply-To :  Sam.Irving@Reg.Organization
     To       :  George Jones <Group@Some-Reg.An-Org>,
                 Al.Neuman@MAD.Publisher
     cc       :  Important folk:
                   Tom Softwood <Balsa@Tree.Root>,
                   "Sam Irving"@Other-Host;,
                 Standard Distribution:
                   /main/davis/people/standard@Other-Host,
                   "<Jones>standard.dist.3"@Tops-20-Host>;
     Comment  :  Sam is away on business. He asked me to handle
                 his mail for him.  He'll be able to provide  a
                 more  accurate  explanation  when  he  returns
                 next week.
     In-Reply-To: <some.string@DBM.Group>, George's message
     X-Special-action:  This is a sample of user-defined field-
                 names.  There could also be a field-name
                 "Special-action", but its name might later be
                 preempted
     Message-ID: <4231.629.XYzi-What@Other-Host>






     August 13, 1982              - 39 -                      RFC #822


 
     Standard for ARPA Internet Text Messages


     B.  SIMPLE FIELD PARSING

          Some mail-reading software systems may wish to perform  only
     minimal  processing,  ignoring  the internal syntax of structured
     field-bodies and treating them the  same  as  unstructured-field-
     bodies.  Such software will need only to distinguish:

         o   Header fields from the message body,

         o   Beginnings of fields from lines which continue fields,

         o   Field-names from field-contents.

          The abbreviated set of syntactic rules  which  follows  will
     suffice  for  this  purpose.  It describes a limited view of mes-
     sages and is a subset of the syntactic rules provided in the main
     part of this specification.  One small exception is that the con-
     tents of field-bodies consist only of text:

     B.1.  SYNTAX


     message         =   *field *(CRLF *text)

     field           =    field-name ":" [field-body] CRLF

     field-name      =  1*<any CHAR, excluding CTLs, SPACE, and ":">

     field-body      =   *text [CRLF LWSP-char field-body]


     B.2.  SEMANTICS

          Headers occur before the message body and are terminated  by
     a null line (i.e., two contiguous CRLFs).

          A line which continues a header field begins with a SPACE or
     HTAB  character,  while  a  line  beginning a field starts with a
     printable character which is not a colon.

          A field-name consists of one or  more  printable  characters
     (excluding  colon,  space, and control-characters).  A field-name
     MUST be contained on one line.  Upper and lower case are not dis-
     tinguished when comparing field-names.







     August 13, 1982              - 40 -                      RFC #822


 
     Standard for ARPA Internet Text Messages


     C.  DIFFERENCES FROM RFC #733

          The following summarizes the differences between this  stan-
     dard  and the one specified in Arpanet Request for Comments #733,
     "Standard for the Format of ARPA  Network  Text  Messages".   The
     differences  are  listed  in the order of their occurrence in the
     current specification.

     C.1.  FIELD DEFINITIONS

     C.1.1.  FIELD NAMES

        These now must be a sequence of  printable  characters.   They
        may not contain any LWSP-chars.

     C.2.  LEXICAL TOKENS

     C.2.1.  SPECIALS

        The characters period ("."), left-square  bracket  ("["),  and
        right-square  bracket ("]") have been added.  For presentation
        purposes, and when passing a specification to  a  system  that
        does  not conform to this standard, periods are to be contigu-
        ous with their surrounding lexical tokens.   No  linear-white-
        space  is  permitted  between them.  The presence of one LWSP-
        char between other tokens is still directed.

     C.2.2.  ATOM

        Atoms may not contain SPACE.

     C.2.3.  SPECIAL TEXT

        ctext and qtext have had backslash ("\") added to the list  of
        prohibited characters.

     C.2.4.  DOMAINS

        The lexical tokens  <domain-literal>  and  <dtext>  have  been
        added.

     C.3.  MESSAGE SPECIFICATION

     C.3.1.  TRACE

        The "Return-path:" and "Received:" fields have been specified.





     August 13, 1982              - 41 -                      RFC #822


 
     Standard for ARPA Internet Text Messages


     C.3.2.  FROM

        The "From" field must contain machine-usable addresses  (addr-
        spec).   Multiple  addresses may be specified, but named-lists
        (groups) may not.

     C.3.3.  RESENT

        The meta-construct of prefacing field names  with  the  string
        "Resent-"  has been added, to indicate that a message has been
        forwarded by an intermediate recipient.

     C.3.4.  DESTINATION

        A message must contain at least one destination address field.
        "To" and "CC" are required to contain at least one address.

     C.3.5.  IN-REPLY-TO

        The field-body is no longer a comma-separated list, although a
        sequence is still permitted.

     C.3.6.  REFERENCE

        The field-body is no longer a comma-separated list, although a
        sequence is still permitted.

     C.3.7.  ENCRYPTED

        A field has been specified that permits  senders  to  indicate
        that the body of a message has been encrypted.

     C.3.8.  EXTENSION-FIELD

        Extension fields are prohibited from beginning with the  char-
        acters "X-".

     C.4.  DATE AND TIME SPECIFICATION

     C.4.1.  SIMPLIFICATION

        Fewer optional forms are permitted  and  the  list  of  three-
        letter time zones has been shortened.

     C.5.  ADDRESS SPECIFICATION






     August 13, 1982              - 42 -                      RFC #822


 
     Standard for ARPA Internet Text Messages


     C.5.1.  ADDRESS

        The use of quoted-string, and the ":"-atom-":" construct, have
        been  removed.   An  address  now  is  either a single mailbox
        reference or is a named list of addresses.  The  latter  indi-
        cates a group distribution.

     C.5.2.  GROUPS

        Group lists are now required to to have a name.   Group  lists
        may not be nested.

     C.5.3.  MAILBOX

        A mailbox specification  may  indicate  a  person's  name,  as
        before.   Such  a  named  list  no longer may specify multiple
        mailboxes and may not be nested.

     C.5.4.  ROUTE ADDRESSING

        Addresses now are taken to be absolute, global specifications,
        independent  of transmission paths.  The <route> construct has
        been provided, to permit explicit specification  of  transmis-
        sion  path.   RFC  #733's  use  of multiple at-signs ("@") was
        intended as a general syntax  for  indicating  routing  and/or
        hierarchical addressing.  The current standard separates these
        specifications and only one at-sign is permitted.

     C.5.5.  AT-SIGN

        The string " at " no longer is used as an  address  delimiter.
        Only at-sign ("@") serves the function.

     C.5.6.  DOMAINS

        Hierarchical, logical name-domains have been added.

     C.6.  RESERVED ADDRESS

     The local-part "Postmaster" has been reserved, so that users  can
     be guaranteed at least one valid address at a site.










     August 13, 1982              - 43 -                      RFC #822


 
     Standard for ARPA Internet Text Messages


     D.  ALPHABETICAL LISTING OF SYNTAX RULES

     address     =  mailbox                      ; one addressee
                 /  group                        ; named list
     addr-spec   =  local-part "@" domain        ; global address
     ALPHA       =  <any ASCII alphabetic character>
                                                 ; (101-132, 65.- 90.)
                                                 ; (141-172, 97.-122.)
     atom        =  1*<any CHAR except specials, SPACE and CTLs>
     authentic   =   "From"       ":"   mailbox  ; Single author
                 / ( "Sender"     ":"   mailbox  ; Actual submittor
                     "From"       ":" 1#mailbox) ; Multiple authors
                                                 ;  or not sender
     CHAR        =  <any ASCII character>        ; (  0-177,  0.-127.)
     comment     =  "(" *(ctext / quoted-pair / comment) ")"
     CR          =  <ASCII CR, carriage return>  ; (     15,      13.)
     CRLF        =  CR LF
     ctext       =  <any CHAR excluding "(",     ; => may be folded
                     ")", "\" & CR, & including
                     linear-white-space>
     CTL         =  <any ASCII control           ; (  0- 37,  0.- 31.)
                     character and DEL>          ; (    177,     127.)
     date        =  1*2DIGIT month 2DIGIT        ; day month year
                                                 ;  e.g. 20 Jun 82
     dates       =   orig-date                   ; Original
                   [ resent-date ]               ; Forwarded
     date-time   =  [ day "," ] date time        ; dd mm yy
                                                 ;  hh:mm:ss zzz
     day         =  "Mon"  / "Tue" /  "Wed"  / "Thu"
                 /  "Fri"  / "Sat" /  "Sun"
     delimiters  =  specials / linear-white-space / comment
     destination =  "To"          ":" 1#address  ; Primary
                 /  "Resent-To"   ":" 1#address
                 /  "cc"          ":" 1#address  ; Secondary
                 /  "Resent-cc"   ":" 1#address
                 /  "bcc"         ":"  #address  ; Blind carbon
                 /  "Resent-bcc"  ":"  #address
     DIGIT       =  <any ASCII decimal digit>    ; ( 60- 71, 48.- 57.)
     domain      =  sub-domain *("." sub-domain)
     domain-literal =  "[" *(dtext / quoted-pair) "]"
     domain-ref  =  atom                         ; symbolic reference
     dtext       =  <any CHAR excluding "[",     ; => may be folded
                     "]", "\" & CR, & including
                     linear-white-space>
     extension-field =
                   <Any field which is defined in a document
                    published as a formal extension to this
                    specification; none will have names beginning
                    with the string "X-">


     August 13, 1982              - 44 -                      RFC #822


 
     Standard for ARPA Internet Text Messages


     field       =  field-name ":" [ field-body ] CRLF
     fields      =    dates                      ; Creation time,
                      source                     ;  author id & one
                    1*destination                ;  address required
                     *optional-field             ;  others optional
     field-body  =  field-body-contents
                    [CRLF LWSP-char field-body]
     field-body-contents =
                   <the ASCII characters making up the field-body, as
                    defined in the following sections, and consisting
                    of combinations of atom, quoted-string, and
                    specials tokens, or else consisting of texts>
     field-name  =  1*<any CHAR, excluding CTLs, SPACE, and ":">
     group       =  phrase ":" [#mailbox] ";"
     hour        =  2DIGIT ":" 2DIGIT [":" 2DIGIT]
                                                 ; 00:00:00 - 23:59:59
     HTAB        =  <ASCII HT, horizontal-tab>   ; (     11,       9.)
     LF          =  <ASCII LF, linefeed>         ; (     12,      10.)
     linear-white-space =  1*([CRLF] LWSP-char)  ; semantics = SPACE
                                                 ; CRLF => folding
     local-part  =  word *("." word)             ; uninterpreted
                                                 ; case-preserved
     LWSP-char   =  SPACE / HTAB                 ; semantics = SPACE
     mailbox     =  addr-spec                    ; simple address
                 /  phrase route-addr            ; name & addr-spec
     message     =  fields *( CRLF *text )       ; Everything after
                                                 ;  first null line
                                                 ;  is message body
     month       =  "Jan"  /  "Feb" /  "Mar"  /  "Apr"
                 /  "May"  /  "Jun" /  "Jul"  /  "Aug"
                 /  "Sep"  /  "Oct" /  "Nov"  /  "Dec"
     msg-id      =  "<" addr-spec ">"            ; Unique message id
     optional-field =
                 /  "Message-ID"        ":"   msg-id
                 /  "Resent-Message-ID" ":"   msg-id
                 /  "In-Reply-To"       ":"  *(phrase / msg-id)
                 /  "References"        ":"  *(phrase / msg-id)
                 /  "Keywords"          ":"  #phrase
                 /  "Subject"           ":"  *text
                 /  "Comments"          ":"  *text
                 /  "Encrypted"         ":" 1#2word
                 /  extension-field              ; To be defined
                 /  user-defined-field           ; May be pre-empted
     orig-date   =  "Date"        ":"   date-time
     originator  =   authentic                   ; authenticated addr
                   [ "Reply-To"   ":" 1#address] )
     phrase      =  1*word                       ; Sequence of words




     August 13, 1982              - 45 -                      RFC #822


 
     Standard for ARPA Internet Text Messages


     qtext       =  <any CHAR excepting <">,     ; => may be folded
                     "\" & CR, and including
                     linear-white-space>
     quoted-pair =  "\" CHAR                     ; may quote any char
     quoted-string = <"> *(qtext/quoted-pair) <">; Regular qtext or
                                                 ;   quoted chars.
     received    =  "Received"    ":"            ; one per relay
                       ["from" domain]           ; sending host
                       ["by"   domain]           ; receiving host
                       ["via"  atom]             ; physical path
                      *("with" atom)             ; link/mail protocol
                       ["id"   msg-id]           ; receiver msg id
                       ["for"  addr-spec]        ; initial form
                        ";"    date-time         ; time received

     resent      =   resent-authentic
                   [ "Resent-Reply-To"  ":" 1#address] )
     resent-authentic =
                 =   "Resent-From"      ":"   mailbox
                 / ( "Resent-Sender"    ":"   mailbox
                     "Resent-From"      ":" 1#mailbox  )
     resent-date =  "Resent-Date" ":"   date-time
     return      =  "Return-path" ":" route-addr ; return address
     route       =  1#("@" domain) ":"           ; path-relative
     route-addr  =  "<" [route] addr-spec ">"
     source      = [  trace ]                    ; net traversals
                      originator                 ; original mail
                   [  resent ]                   ; forwarded
     SPACE       =  <ASCII SP, space>            ; (     40,      32.)
     specials    =  "(" / ")" / "<" / ">" / "@"  ; Must be in quoted-
                 /  "," / ";" / ":" / "\" / <">  ;  string, to use
                 /  "." / "[" / "]"              ;  within a word.
     sub-domain  =  domain-ref / domain-literal
     text        =  <any CHAR, including bare    ; => atoms, specials,
                     CR & bare LF, but NOT       ;  comments and
                     including CRLF>             ;  quoted-strings are
                                                 ;  NOT recognized.
     time        =  hour zone                    ; ANSI and Military
     trace       =    return                     ; path to sender
                    1*received                   ; receipt tags
     user-defined-field =
                   <Any field which has not been defined
                    in this specification or published as an
                    extension to this specification; names for
                    such fields must be unique and may be
                    pre-empted by published extensions>
     word        =  atom / quoted-string




     August 13, 1982              - 46 -                      RFC #822


 
     Standard for ARPA Internet Text Messages


     zone        =  "UT"  / "GMT"                ; Universal Time
                                                 ; North American : UT
                 /  "EST" / "EDT"                ;  Eastern:  - 5/ - 4
                 /  "CST" / "CDT"                ;  Central:  - 6/ - 5
                 /  "MST" / "MDT"                ;  Mountain: - 7/ - 6
                 /  "PST" / "PDT"                ;  Pacific:  - 8/ - 7
                 /  1ALPHA                       ; Military: Z = UT;
     <">         =  <ASCII quote mark>           ; (     42,      34.)











































     August 13, 1982              - 47 -                      RFC #822

OpenPOWER on IntegriCloud