1.\" Copyright (c) 1983, 1987, 1990, 1993 2.\" The Regents of the University of California. All rights reserved. 3.\" 4.\" %sccs.include.redist.man% 5.\" 6.\" @(#)mailaddr.7 8.1 (Berkeley) 06/16/93 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 Internet 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, a valid address is: 22.Pp 23.Dl eric@CS.Berkeley.EDU 24.Pp 25Unlike some other forms of addressing, domains do not imply any routing. 26Thus, although this address is specified as an Internet address, it might 27travel by an alternate route if that were more convenient or efficient. 28For example, at Berkeley, the associated message would probably go directly 29to CS over the Ethernet rather than going via the Berkeley Internet 30gateway. 31.Ss Abbreviation. 32Under certain circumstances it may not be necessary to type the entire 33domain name. In general, anything following the first dot may be omitted 34if it is the same as the domain from which you are sending the message. 35For example, a user on ``calder.berkeley.edu'' could send to ``eric@CS'' 36without adding the ``berkeley.edu'' since it is the same on both sending 37and receiving hosts. 38.Ss Compatibility. 39.Pp 40Certain old address formats are converted to the new format to provide 41compatibility with the previous mail system. In particular, 42.Pp 43.Dl user@host 44.Pp 45and 46.Dl user@host.domain 47.Pp 48are allowed; 49.Pp 50.Dl host.domain!user 51.Pp 52is converted to 53.Pp 54.Dl user@host.domain 55.Pp 56and 57.Pp 58.Dl host!user 59.Pp 60is converted to 61.Pp 62.Dl user@host.UUCP 63.Pp 64This is normally converted back to the ``host!user'' form before being sent 65on for compatibility with older UUCP hosts. 66.Pp 67.Ss Case Distinctions. 68.Pp 69Domain names (i.e., anything after the ``@'' sign) may be given in any mixture 70of upper and lower case with the exception of UUCP hostnames. Most hosts 71accept any combination of case in user names, with the notable exception of 72MULTICS sites. 73.Ss Route-addrs. 74.Pp 75Under some circumstances it may be necessary to route a message through 76several hosts to get it to the final destination. Normally this routing 77is done automatically, but sometimes it is desirable to route the message 78manually. Addresses which show these relays are termed ``route-addrs.'' 79These use the syntax: 80.Pp 81.Dl <@hosta,@hostb:user@hostc> 82.Pp 83This specifies that the message should be sent to hosta, from there to hostb, 84and finally to hostc. This path is forced even if there is a more efficient 85path to hostc. 86.Pp 87Route-addrs occur frequently on return addresses, since these are generally 88augmented by the software at each host. It is generally possible to ignore 89all but the ``user@hostc'' part of the address to determine the actual 90sender. 91.Pp 92[Note: the route-addr syntax is officially deprecated 93in RFC 1123 and should not be used.] 94.Pp 95Many sites also support the ``percent hack'' for simplistic routing: 96.Pp 97.Dl user%hostc%hostb@hosta 98.Pp 99is routed as indicated in the previous example. 100.Ss Postmaster. 101.Pp 102Every site is required to have a user or user alias designated ``postmaster'' 103to which problems with the mail system may be addressed. 104.Ss Other Networks. 105.Pp 106Some other networks can be reached by giving the name of the network as the 107last component of the domain. 108.Em This is not a standard feature 109and may 110not be supported at all sites. For example, messages to CSNET or BITNET sites 111can often be sent to ``user@host.CSNET'' or ``user@host.BITNET'' respectively. 112.Sh SEE ALSO 113.Xr mail 1 , 114.Xr sendmail 8 ; 115.br 116Crocker, D. H., 117.Em Standard for the Format of Arpa Internet Text Messages, 118RFC822. 119.Sh HISTORY 120.Nm Mailaddr 121appeared in 4.2 BSD. 122.Sh BUGS 123The RFC822 group syntax (``group:user1,user2,user3;'') is not supported 124except in the special case of ``group:;'' because of a conflict with old 125berknet-style addresses. 126.Pp 127Route-Address syntax is grotty. 128.Pp 129UUCP- and Internet-style addresses do not coexist politely. 130