1.\" Copyright (c) 1983, 1987, 1990 The Regents of the University of California. 2.\" All rights reserved. 3.\" 4.\" %sccs.include.redist.man% 5.\" 6.\" @(#)mailaddr.7 6.6 (Berkeley) 06/24/90 7.\" 8.Dd 9.Dt MAILADDR 7 10.Os BSD 4.2 11.Sh NAME 12.Nm mailaddr 13.Nd mail addressing description 14.Sh DESCRIPTION 15Mail addresses are based on the ARPANET protocol listed at the end of this 16manual page. These addresses are in the general format 17.Pp 18.Dl user@domain 19.Pp 20where a domain is a hierarchical dot separated list of subdomains. For 21example, the address 22.Pp 23.Dl eric@monet.berkeley.edu 24.Pp 25is normally interpreted from right to left: the message should go to the 26ARPA name tables (which do not correspond exactly to the physical ARPANET), 27then to the Berkeley gateway, after which it should go to the local host 28monet. When the message reaches monet it is delivered to the user ``eric''. 29.Pp 30Unlike some other forms of addressing, this does not imply any routing. 31Thus, although this address is specified as an ARPA address, it might 32travel by an alternate route if that were more convenient or efficient. 33For example, at Berkeley, the associated message would probably go directly 34to monet over the Ethernet rather than going via the Berkeley ARPANET 35gateway. 36.Ss Abbreviation. 37Under certain circumstances it may not be necessary to type the entire 38domain name. In general, anything following the first dot may be omitted 39if it is the same as the domain from which you are sending the message. 40For example, a user on ``calder.berkeley.edu'' could send to ``eric@monet'' 41without adding the ``berkeley.edu'' since it is the same on both sending 42and receiving hosts. 43.Pp 44Certain other abbreviations may be permitted as special cases. For 45example, at Berkeley, ARPANET hosts may be referenced without adding 46the ``berkeley.edu'' as long as their names do not conflict with a local 47host name. 48.Ss Compatibility. 49.Pp 50Certain old address formats are converted to the new format to provide 51compatibility with the previous mail system. In particular, 52.Pp 53.Dl user@host.ARPA 54.Pp 55is allowed and 56.Pp 57.Dl host:user 58.Pp 59is converted to 60.Pp 61.Dl user@host 62.Pp 63to be consistent with the 64.Xr rcp 1 65command. 66.Pp 67Also, the syntax 68.Pp 69.Dl host!user 70.Pp 71is converted to: 72.Pp 73.Dl user@host.UUCP 74.Pp 75This is normally converted back to the ``host!user'' form before being sent 76on for compatibility with older UUCP hosts. 77.Pp 78The current implementation is not able to route messages automatically through 79the UUCP network. Until that time you must explicitly tell the mail system 80which hosts to send your message through to get to your final destination. 81.Ss Case Distinctions. 82.Pp 83Domain names (i.e., anything after the ``@'' sign) may be given in any mixture 84of upper and lower case with the exception of UUCP hostnames. Most hosts 85accept any combination of case in user names, with the notable exception of 86MULTICS sites. 87.Ss Route-addrs. 88.Pp 89Under some circumstances it may be necessary to route a message through 90several hosts to get it to the final destination. Normally this routing 91is done automatically, but sometimes it is desirable to route the message 92manually. Addresses which show these relays are termed ``route-addrs.'' 93These use the syntax: 94.Pp 95.Dl <@hosta,@hostb:user@hostc> 96.Pp 97This specifies that the message should be sent to hosta, from there to hostb, 98and finally to hostc. This path is forced even if there is a more efficient 99path to hostc. 100.Pp 101Route-addrs occur frequently on return addresses, since these are generally 102augmented by the software at each host. It is generally possible to ignore 103all but the ``user@domain'' part of the address to determine the actual 104sender. 105.Ss Postmaster. 106.Pp 107Every site is required to have a user or user alias designated ``postmaster'' 108to which problems with the mail system may be addressed. 109.Ss Other Networks. 110.Pp 111Some other networks can be reached by giving the name of the network as the 112last component of the domain. 113.Em This is not a standard feature 114and may 115not be supported at all sites. For example, messages to CSNET or BITNET sites 116can often be sent to ``user@host.CSNET'' or ``user@host.BITNET'' respectively. 117.Sh SEE ALSO 118.Xr mail 1 , 119.Xr sendmail 8 ; 120.br 121Crocker, D. H., 122.Em Standard for the Format of Arpa Internet Text Messages, 123RFC822. 124.Sh HISTORY 125.Nm Mailaddr 126appeared in 4.2 BSD. 127.Sh BUGS 128The RFC822 group syntax (``group:user1,user2,user3;'') is not supported 129except in the special case of ``group:;'' because of a conflict with old 130berknet-style addresses. 131.Pp 132Route-Address syntax is grotty. 133.Pp 134UUCP- and ARPANET-style addresses do not coexist politely. 135