[0m


MAILADDR(7)	    UNIX Programmer's Manual	      MAILADDR(7)



[1mNAME
     [0mmailaddr - mail addressing description

[1mDESCRIPTION
     [0mMail 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.

     [1mAbbreviation.

     [0mUnder 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.

     [1mCompatibility.

     [0mCertain old address formats are converted to the new format
     to provide compatibility with the previous mail system.  In
     particular,





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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.

     [1mCase Distinctions.

     [0mDomain 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.

     [1mDifferences with ARPA Protocols.

     [0mAlthough 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.



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     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.

     [1mRoute-addrs.

     [0mUnder 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.

     [1mPostmaster.

     [0mEvery site is required to have a user or user alias desig-
     nated ``postmaster'' to which problems with the mail system
     may be addressed.

     [1mOther Networks.

     [0mSome 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.

[1mBERKELEY
     [0mThe following comments apply only to the Berkeley environ-
     ment.

     [1mWhat's My Address?

     [0mIf you are on a local machine, say monet, your address is

	       yourname@monet.Berkeley.ARPA





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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

     [1mComputer Center.

     [0mThe 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.

[1mBUGS
     [0mThe 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.

[1mSEE ALSO
     [0mmail(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.













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