1MAILADDR(7) Miscellaneous Information Manual MAILADDR(7)
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6 mailaddr - mail addressing description
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9 Mail addresses are based on the ARPANET protocol listed at the end of
10 this manual page. These addresses are in the general format
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12 user@domain
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14 where a domain is a hierarchical dot separated list of subdomains. For
15 example, the address
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17 eric@monet.berkeley.edu
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19 is normally interpreted from right to left: the message should go to
20 the ARPA name tables (which do not correspond exactly to the physical
21 ARPANET), then to the Berkeley gateway, after which it should go to the
22 local host monet. When the message reaches monet it is delivered to
23 the user ``eric''.
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25 Unlike some other forms of addressing, this does not imply any routing.
26 Thus, although this address is specified as an ARPA address, it might
27 travel by an alternate route if that were more convenient or efficient.
28 For example, at Berkeley, the associated message would probably go
29 directly to monet over the Ethernet rather than going via the Berkeley
30 ARPANET gateway.
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32 Abbreviation.
33 Under certain circumstances it may not be necessary to type the entire
34 domain name. In general, anything following the first dot may be omit‐
35 ted if it is the same as the domain from which you are sending the mes‐
36 sage. For example, a user on ``calder.berkeley.edu'' could send to
37 ``eric@monet'' without adding the ``berkeley.edu'' since it is the same
38 on both sending and receiving hosts.
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40 Certain other abbreviations may be permitted as special cases. For
41 example, at Berkeley, ARPANET hosts may be referenced without adding
42 the ``berkeley.edu'' as long as their names do not conflict with a
43 local host name.
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45 Compatibility.
46 Certain old address formats are converted to the new format to provide
47 compatibility with the previous mail system. In particular,
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49 user@host.ARPA
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51 is allowed and
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53 host:user
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55 is converted to
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57 user@host
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59 to be consistent with the rcp(1) command.
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61 Also, the syntax
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63 host!user
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65 is converted to:
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67 user@host.UUCP
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69 This is normally converted back to the ``host!user'' form before being
70 sent on for compatibility with older UUCP hosts.
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72 The current implementation is not able to route messages automatically
73 through the UUCP network. Until that time you must explicitly tell the
74 mail system which hosts to send your message through to get to your
75 final destination.
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77 Case Distinctions.
78 Domain names (i.e., anything after the ``@'' sign) may be given in any
79 mixture of upper and lower case with the exception of UUCP hostnames.
80 Most hosts accept any combination of case in user names, with the
81 notable exception of MULTICS sites.
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83 Route-addrs.
84 Under some circumstances it may be necessary to route a message through
85 several hosts to get it to the final destination. Normally this rout‐
86 ing is done automatically, but sometimes it is desirable to route the
87 message manually. Addresses which show these relays are termed
88 ``route-addrs.'' These use the syntax:
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90 <@hosta,@hostb:user@hostc>
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92 This specifies that the message should be sent to hosta, from there to
93 hostb, and finally to hostc. This path is forced even if there is a
94 more efficient path to hostc.
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96 Route-addrs occur frequently on return addresses, since these are gen‐
97 erally augmented by the software at each host. It is generally possi‐
98 ble to ignore all but the ``user@domain'' part of the address to deter‐
99 mine the actual sender.
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101 Postmaster.
102 Every site is required to have a user or user alias designated ``post‐
103 master'' to which problems with the mail system may be addressed.
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105 Other Networks.
106 Some other networks can be reached by giving the name of the network as
107 the last component of the domain. This is not a standard feature and
108 may not be supported at all sites. For example, messages to CSNET or
109 BITNET sites can often be sent to ``user@host.CSNET'' or
110 ``user@host.BITNET'' respectively.
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113 The RFC822 group syntax (``group:user1,user2,user3;'') is not supported
114 except in the special case of ``group:;'' because of a conflict with
115 old berknet-style addresses.
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117 Route-Address syntax is grotty.
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119 UUCP- and ARPANET-style addresses do not coexist politely.
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122 mail(1), sendmail(8); Crocker, D. H., Standard for the Format of Arpa
123 Internet Text Messages, RFC822.
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1274.2 Berkeley Distribution July 27, 1987 MAILADDR(7)