Relay-Version: version B 2.10 5/3/83; site utzoo.UUCP
Posting-Version: version B 2.10.2 9/18/84 SMI; site sun.uucp
Path: utzoo!watmath!clyde!cbosgd!ihnp4!ucbvax!decvax!decwrl!sun!guy
From: guy@sun.uucp (Guy Harris)
Newsgroups: net.mail
Subject: Re: Standardising the "postmaster" concept
Message-ID: <2767@sun.uucp>
Date: Sat, 7-Sep-85 18:15:25 EDT
Article-I.D.: sun.2767
Posted: Sat Sep  7 18:15:25 1985
Date-Received: Mon, 9-Sep-85 04:23:29 EDT
References: <426@mungunni.OZ> <10298@ucbvax.ARPA>
Organization: Sun Microsystems, Inc.
Lines: 39

> `Postmaster' as a valid mail address is required by the ARPA Internet Mail
> Standard, RFC822, so all ARPA Internet sites will have a `postmaster',
> regardless of whether they have netnews or not.

4.xBSD sites (x >= 2) also have "postmaster" as an alias in their
/usr/lib/aliases file, whether they're on the internet or not, unless
they've deleted it (which they shouldn't do).  Sites running a UNIX which
comes with "sendmail" may also have "postmaster" in their /usr/lib/aliases
file.

> Unfortunately for this idea, all of the versions of UNIX, other than
> the ones that come from Berkeley (2 & 4 BSD), have the most bletcherous
> mailers that it would ever be your misfortune to encounter, which,
> without exception, do not support the concept of an `alias' (e.g.
> ucbvax!usenet, ucbvax!erik, and a few other things, can all point to
> ucbvax!fair, without existing as entries in /etc/passwd).

To clarify a little: "mailer" here doesn't refer to the program you use to
read and send mail messages (System V has a better mailer called "mailx";
the reason it's better is that it's a hacked-up version of the Berkeley
"Mail", although they only mention this fact in comments in the source code -
no credit where credit is due...), but to the program which does mail
delivery and routing.  "Sendmail" and the earlier "delivermail" have an
aliasing capability like this.  Without getting into the endless debate as
to whether "sendmail" is the answer to a maiden's prayer or the horror of
the century, having the ability to do such aliasing is extremely useful once
your Email system gets above a certain level of complexity.

One place where it's *very* useful is if you have a large network of
machines and one machine which acts as a gateway to a large mail network,
like UUCP or the Internet.  You can have everybody mail to, say, "user@sun"
and use the alias mechanism to route mail to the user's own machine.  This
hides the details of your internal network from the rest of the world, who
probably doesn't want to know those details.  Using "sendmail", you can also
rewrite the "From" addresses of outgoing mail so that it looks like it comes
from "user@sun" or whatever, thus completely hiding your internal machines
from the outside world.  (Yes, I know Sun doesn't do that.)

	Guy Harris