4.3BSD-UWisc/man/cat7/mailaddr.7
MAILADDR(7) UNIX Programmer's Manual MAILADDR(7)
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 sub-
domains. For example, the address
eric@monet.Berkeley.ARPA
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 gate-
way, 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 following the
first dot may be omitted if it is the same as the domain
from which you are sending the message. For example, a user
on ``calder.Berkeley.ARPA'' could send to ``eric@monet''
without adding the ``.Berkeley.ARPA'' 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 can be refer-
enced without adding the ``.ARPA'' as long as their names do
not conflict with a local host name.
Compatibility.
Certain old address formats are converted to the new format
to provide compatibility with the previous mail system. In
particular,
Printed 12/27/86 May 6, 1986 1
MAILADDR(7) UNIX Programmer's Manual MAILADDR(7)
host:user
is converted to
user@host
to be consistent with the _r_c_p(1C) 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 destination.
Case Distinctions.
Domain names (i.e., anything after the ``@'' sign) may be
given in any mixture of upper and lower case with the excep-
tion of UUCP hostnames. Most hosts accept any combination
of case in user names, with the notable exception of MULTICS
sites.
Differences with ARPA Protocols.
Although the UNIX addressing scheme is based on the ARPA
mail addressing protocols, there are some significant
differences.
At the time of this writing DARPA is converting to real
domains. The following rules may be useful:
o+ The syntax ``user@host.ARPA'' is being split up into
``user@host.COM'', ``user@host.GOV'', and ``user@host.EDU''
for commercial, government, and educational institutions
respectively.
o+ The syntax ``user@host'' (with no dots) has traditionally
referred to the ARPANET. In the future this semantic will
not be continued - instead, the host will be assumed to be
in your organization. You should start using one of the
syntaxes above.
Printed 12/27/86 May 6, 1986 2
MAILADDR(7) UNIX Programmer's Manual MAILADDR(7)
o+ Host names of the form ``ORG-NAME'' (e.g., MIT-MC or CMU-
CS-A) will be changing to ``NAME.ORG.XXX'' (where `XXX' is
COM, GOV, or EDU). For example, MIT-MC will change to
MC.MIT.EDU. In some cases names will be split apart even if
they do not have dashes. For example, USC-ISIF will prob-
ably change to F.ISI.USC.EDU.
Route-addrs.
Under some circumstances it may be necessary to route a mes-
sage through several hosts to get it to the final destina-
tion. Normally this routing is done automatically, but
sometimes it is desirable to route the message manually.
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@host''
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. _T_h_i_s _i_s _n_o_t _a
_s_t_a_n_d_a_r_d _f_e_a_t_u_r_e 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.
BERKELEY
The following comments apply only to the Berkeley environ-
ment.
What's My Address?
If you are on a local machine, say monet, your address is
yourname@monet.Berkeley.ARPA
Printed 12/27/86 May 6, 1986 3
MAILADDR(7) UNIX Programmer's Manual MAILADDR(7)
However, since most of the world does not have the new
software in place yet, you will have to give correspondents
slightly different addresses. From the ARPANET, your
address would be:
yourname%monet@Berkeley.ARPA
From UUCP, your address would be:
ucbvax!yourname%monet
Computer Center.
The Berkeley Computer Center is in a subdomain of Berkeley.
Messages to the computer center should be addressed to:
user%host.CC@Berkeley.ARPA
The alternate syntax:
user@host.CC
may be used if the message is sent from inside Berkeley.
For the time being Computer Center hosts are known within
the Berkeley domain, i.e., the ``.CC'' is optional. How-
ever, it is likely that this situation will change with time
as both the Computer Science department and the Computer
Center grow.
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., _S_t_a_n_d_a_r_d _f_o_r _t_h_e _F_o_r_-
_m_a_t _o_f _A_r_p_a _I_n_t_e_r_n_e_t _T_e_x_t _M_e_s_s_a_g_e_s, RFC822.
Printed 12/27/86 May 6, 1986 4