1.\" Copyright (c) 1983, 1987, 1990 The Regents of the University of California. 2.\" All rights reserved. 3.\" 4.\" Redistribution and use in source and binary forms, with or without 5.\" modification, are permitted provided that the following conditions 6.\" are met: 7.\" 1. Redistributions of source code must retain the above copyright 8.\" notice, this list of conditions and the following disclaimer. 9.\" 2. Redistributions in binary form must reproduce the above copyright 10.\" notice, this list of conditions and the following disclaimer in the 11.\" documentation and/or other materials provided with the distribution. 12.\" 3. All advertising materials mentioning features or use of this software 13.\" must display the following acknowledgement: 14.\" This product includes software developed by the University of 15.\" California, Berkeley and its contributors. 16.\" 4. Neither the name of the University nor the names of its contributors 17.\" may be used to endorse or promote products derived from this software 18.\" without specific prior written permission. 19.\" 20.\" THIS SOFTWARE IS PROVIDED BY THE REGENTS AND CONTRIBUTORS ``AS IS'' AND 21.\" ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE 22.\" IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE 23.\" ARE DISCLAIMED. IN NO EVENT SHALL THE REGENTS OR CONTRIBUTORS BE LIABLE 24.\" FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL 25.\" DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS 26.\" OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) 27.\" HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT 28.\" LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY 29.\" OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF 30.\" SUCH DAMAGE. 31.\" 32.\" @(#)mailaddr.7 6.6 (Berkeley) 6/24/90 33.\" 34.Dd June 24, 1990 35.Dt MAILADDR 7 36.Os BSD 4.2 37.Sh NAME 38.Nm mailaddr 39.Nd mail addressing description 40.Sh DESCRIPTION 41Mail addresses are based on the ARPANET protocol listed at the end of this 42manual page. These addresses are in the general format 43.Pp 44.Dl user@domain 45.Pp 46where a domain is a hierarchical dot separated list of subdomains. For 47example, the address 48.Pp 49.Dl eric@monet.berkeley.edu 50.Pp 51is normally interpreted from right to left: the message should go to the 52ARPA name tables (which do not correspond exactly to the physical ARPANET), 53then to the Berkeley gateway, after which it should go to the local host 54monet. When the message reaches monet it is delivered to the user ``eric''. 55.Pp 56Unlike some other forms of addressing, this does not imply any routing. 57Thus, although this address is specified as an ARPA address, it might 58travel by an alternate route if that were more convenient or efficient. 59For example, at Berkeley, the associated message would probably go directly 60to monet over the Ethernet rather than going via the Berkeley ARPANET 61gateway. 62.Ss Abbreviation. 63Under certain circumstances it may not be necessary to type the entire 64domain name. In general, anything following the first dot may be omitted 65if it is the same as the domain from which you are sending the message. 66For example, a user on ``calder.berkeley.edu'' could send to ``eric@monet'' 67without adding the ``berkeley.edu'' since it is the same on both sending 68and receiving hosts. 69.Pp 70Certain other abbreviations may be permitted as special cases. For 71example, at Berkeley, ARPANET hosts may be referenced without adding 72the ``berkeley.edu'' as long as their names do not conflict with a local 73host name. 74.Ss Compatibility. 75.Pp 76Certain old address formats are converted to the new format to provide 77compatibility with the previous mail system. In particular, 78.Pp 79.Dl user@host.ARPA 80.Pp 81is allowed and 82.Pp 83.Dl host:user 84.Pp 85is converted to 86.Pp 87.Dl user@host 88.Pp 89to be consistent with the 90.Xr rcp 1 91command. 92.Pp 93Also, the syntax 94.Pp 95.Dl host!user 96.Pp 97is converted to: 98.Pp 99.Dl user@host.UUCP 100.Pp 101This is normally converted back to the ``host!user'' form before being sent 102on for compatibility with older UUCP hosts. 103.Pp 104The current implementation is not able to route messages automatically through 105the UUCP network. Until that time you must explicitly tell the mail system 106which hosts to send your message through to get to your final destination. 107.Ss Case Distinctions. 108.Pp 109Domain names (i.e., anything after the ``@'' sign) may be given in any mixture 110of upper and lower case with the exception of UUCP hostnames. Most hosts 111accept any combination of case in user names, with the notable exception of 112MULTICS sites. 113.Ss Route-addrs. 114.Pp 115Under some circumstances it may be necessary to route a message through 116several hosts to get it to the final destination. Normally this routing 117is done automatically, but sometimes it is desirable to route the message 118manually. Addresses which show these relays are termed ``route-addrs.'' 119These use the syntax: 120.Pp 121.Dl <@hosta,@hostb:user@hostc> 122.Pp 123This specifies that the message should be sent to hosta, from there to hostb, 124and finally to hostc. This path is forced even if there is a more efficient 125path to hostc. 126.Pp 127Route-addrs occur frequently on return addresses, since these are generally 128augmented by the software at each host. It is generally possible to ignore 129all but the ``user@domain'' part of the address to determine the actual 130sender. 131.Ss Postmaster. 132.Pp 133Every site is required to have a user or user alias designated ``postmaster'' 134to which problems with the mail system may be addressed. 135.Ss Other Networks. 136.Pp 137Some other networks can be reached by giving the name of the network as the 138last component of the domain. 139.Em This is not a standard feature 140and may 141not be supported at all sites. For example, messages to CSNET or BITNET sites 142can often be sent to ``user@host.CSNET'' or ``user@host.BITNET'' respectively. 143.Sh SEE ALSO 144.Xr mail 1 , 145.Xr sendmail 8 ; 146.br 147Crocker, D. H., 148.Em Standard for the Format of Arpa Internet Text Messages, 149RFC822. 150.Sh HISTORY 151.Nm Mailaddr 152appeared in 4.2 BSD. 153.Sh BUGS 154The RFC822 group syntax (``group:user1,user2,user3;'') is not supported 155except in the special case of ``group:;'' because of a conflict with old 156berknet-style addresses. 157.Pp 158Route-Address syntax is grotty. 159.Pp 160UUCP- and ARPANET-style addresses do not coexist politely. 161