mailaddr
Hurricane Electric Internet Services
NAME
mailaddr - mail addressing description
DESCRIPTION
Mail addresses are based on the ARPANET protocol listed at
the end of this manual page. These addresses are in the
general format
user@domain
where a domain is a hierarchical dot separated list of
subdomains. For example, the address
eric@monet.berkeley.edu
is normally interpreted from right to left: the message
should go to the ARPA name tables (which do not correspond
exactly to the physical ARPANET), then to the Berkeley
gateway, after which it should go to the local host monet.
When the message reaches monet it is delivered to the user
``eric''.
Unlike some other forms of addressing, this does not imply
any routing. Thus, although this address is specified as
an ARPA address, it might travel by an alternate route if
that were more convenient or efficient. For example, at
Berkeley, the associated message would probably go
directly to monet over the Ethernet rather than going via
the Berkeley ARPANET gateway.
Abbreviation.
Under certain circumstances it may not be necessary to
type the entire domain name. In general, anything follow-
ing the first dot may be omitted if it is the same as the
domain from which you are sending the message. For exam-
ple, a user on ``calder.berkeley.edu'' could send to
``eric@monet'' without adding the ``berkeley.edu'' since
it is the same on both sending and receiving hosts.
Certain other abbreviations may be permitted as special
cases. For example, at Berkeley, ARPANET hosts may be
referenced without adding the ``berkeley.edu'' as long as
their names do not conflict with a local host name.
Compatibility.
Certain old address formats are converted to the new for-
mat to provide compatibility with the previous mail sys-
tem. In particular,
user@host.ARPA
is allowed and
host:user
is converted to
user@host
to be consistent with the rcp(1) command.
Also, the syntax
host!user
is converted to:
user@host.UUCP
This is normally converted back to the ``host!user'' form
before being sent on for compatibility with older UUCP
hosts.
The current implementation is not able to route messages
automatically through the UUCP network. Until that time
you must explicitly tell the mail system which hosts to
send your message through to get to your final destina-
tion.
Case Distinctions.
Domain names (i.e., anything after the ``@'' sign) may be
given in any mixture of upper and lower case with the
exception of UUCP hostnames. Most hosts accept any combi-
nation of case in user names, with the notable exception
of MULTICS sites.
Route-addrs.
Under some circumstances it may be necessary to route a
message through several hosts to get it to the final des-
tination. Normally this routing is done automatically,
but sometimes it is desirable to route the message manu-
ally. Addresses which show these relays are termed
``route-addrs.'' These use the syntax:
<@hosta,@hostb:user@hostc>
This specifies that the message should be sent to hosta,
from there to hostb, and finally to hostc. This path is
forced even if there is a more efficient path to hostc.
Route-addrs occur frequently on return addresses, since
these are generally augmented by the software at each
host. It is generally possible to ignore all but the
``user@domain'' part of the address to determine the
actual sender.
Postmaster.
Every site is required to have a user or user alias desig-
nated ``postmaster'' to which problems with the mail
system may be addressed.
Other Networks.
Some other networks can be reached by giving the name of
the network as the last component of the domain. This is
not a standard feature and may not be supported at all
sites. For example, messages to CSNET or BITNET sites can
often be sent to ``user@host.CSNET'' or
``user@host.BITNET'' respectively.
BUGS
The RFC822 group syntax (``group:user1,user2,user3;'') is
not supported except in the special case of ``group:;''
because of a conflict with old berknet-style addresses.
Route-Address syntax is grotty.
UUCP- and ARPANET-style addresses do not coexist politely.
SEE ALSO
mail(1), sendmail(8); Crocker, D. H., Standard for the
Format of Arpa Internet Text Messages, RFC822.
Hurricane Electric Internet Services
Copyright (C) 1998
Hurricane Electric.
All Rights Reserved.