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.\" from: @(#)mailaddr.7 6.6 (Berkeley) 6/24/90 33.\" $Id: mailaddr.7,v 1.2 1993/08/01 07:35:02 mycroft Exp $ 34.\" 35.Dd June 24, 1990 36.Dt MAILADDR 7 37.Os BSD 4.2 38.Sh NAME 39.Nm mailaddr 40.Nd mail addressing description 41.Sh DESCRIPTION 42Mail addresses are based on the ARPANET protocol listed at the end of this 43manual page. These addresses are in the general format 44.Pp 45.Dl user@domain 46.Pp 47where a domain is a hierarchical dot separated list of subdomains. For 48example, the address 49.Pp 50.Dl eric@monet.berkeley.edu 51.Pp 52is normally interpreted from right to left: the message should go to the 53ARPA name tables (which do not correspond exactly to the physical ARPANET), 54then to the Berkeley gateway, after which it should go to the local host 55monet. When the message reaches monet it is delivered to the user ``eric''. 56.Pp 57Unlike some other forms of addressing, this does not imply any routing. 58Thus, although this address is specified as an ARPA address, it might 59travel by an alternate route if that were more convenient or efficient. 60For example, at Berkeley, the associated message would probably go directly 61to monet over the Ethernet rather than going via the Berkeley ARPANET 62gateway. 63.Ss Abbreviation. 64Under certain circumstances it may not be necessary to type the entire 65domain name. In general, anything following the first dot may be omitted 66if it is the same as the domain from which you are sending the message. 67For example, a user on ``calder.berkeley.edu'' could send to ``eric@monet'' 68without adding the ``berkeley.edu'' since it is the same on both sending 69and receiving hosts. 70.Pp 71Certain other abbreviations may be permitted as special cases. For 72example, at Berkeley, ARPANET hosts may be referenced without adding 73the ``berkeley.edu'' as long as their names do not conflict with a local 74host name. 75.Ss Compatibility. 76.Pp 77Certain old address formats are converted to the new format to provide 78compatibility with the previous mail system. In particular, 79.Pp 80.Dl user@host.ARPA 81.Pp 82is allowed and 83.Pp 84.Dl host:user 85.Pp 86is converted to 87.Pp 88.Dl user@host 89.Pp 90to be consistent with the 91.Xr rcp 1 92command. 93.Pp 94Also, the syntax 95.Pp 96.Dl host!user 97.Pp 98is converted to: 99.Pp 100.Dl user@host.UUCP 101.Pp 102This is normally converted back to the ``host!user'' form before being sent 103on for compatibility with older UUCP hosts. 104.Pp 105The current implementation is not able to route messages automatically through 106the UUCP network. Until that time you must explicitly tell the mail system 107which hosts to send your message through to get to your final destination. 108.Ss Case Distinctions. 109.Pp 110Domain names (i.e., anything after the ``@'' sign) may be given in any mixture 111of upper and lower case with the exception of UUCP hostnames. Most hosts 112accept any combination of case in user names, with the notable exception of 113MULTICS sites. 114.Ss Route-addrs. 115.Pp 116Under some circumstances it may be necessary to route a message through 117several hosts to get it to the final destination. Normally this routing 118is done automatically, but sometimes it is desirable to route the message 119manually. Addresses which show these relays are termed ``route-addrs.'' 120These use the syntax: 121.Pp 122.Dl <@hosta,@hostb:user@hostc> 123.Pp 124This specifies that the message should be sent to hosta, from there to hostb, 125and finally to hostc. This path is forced even if there is a more efficient 126path to hostc. 127.Pp 128Route-addrs occur frequently on return addresses, since these are generally 129augmented by the software at each host. It is generally possible to ignore 130all but the ``user@domain'' part of the address to determine the actual 131sender. 132.Ss Postmaster. 133.Pp 134Every site is required to have a user or user alias designated ``postmaster'' 135to which problems with the mail system may be addressed. 136.Ss Other Networks. 137.Pp 138Some other networks can be reached by giving the name of the network as the 139last component of the domain. 140.Em This is not a standard feature 141and may 142not be supported at all sites. For example, messages to CSNET or BITNET sites 143can often be sent to ``user@host.CSNET'' or ``user@host.BITNET'' respectively. 144.Sh SEE ALSO 145.Xr mail 1 , 146.Xr sendmail 8 ; 147.br 148Crocker, D. H., 149.Em Standard for the Format of Arpa Internet Text Messages, 150RFC822. 151.Sh HISTORY 152.Nm Mailaddr 153appeared in 4.2 BSD. 154.Sh BUGS 155The RFC822 group syntax (``group:user1,user2,user3;'') is not supported 156except in the special case of ``group:;'' because of a conflict with old 157berknet-style addresses. 158.Pp 159Route-Address syntax is grotty. 160.Pp 161UUCP- and ARPANET-style addresses do not coexist politely. 162