1MAILADDR(7)            Miscellaneous Information Manual            MAILADDR(7)
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NAME

6       mailaddr - mail addressing description
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DESCRIPTION

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
13
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.
31
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.
44
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.
60
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.
76
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.
82
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:
89
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.
95
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.
100
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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BUGS

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.
118
119       UUCP- and ARPANET-style addresses do not coexist politely.
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SEE ALSO

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)
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