Path: utzoo!utgpu!news-server.csri.toronto.edu!mailrus!uwm.edu!wuarchive!cs.utexas.edu!romp!auschs!awdprime!sandino.austin.ibm.com!jeffe
From: jeffe@sandino.austin.ibm.com (Peter Jeffe 512.823.4091)
Newsgroups: comp.unix.aix
Subject: Re: Mail problem in AIX PS/2 V1.2
Keywords: sendmail.cf aix ps/2 Cw aliases self
Message-ID: <3446@awdprime.UUCP>
Date: 8 Sep 90 21:37:42 GMT
References: <5050@mit-caf.MIT.EDU> <1990Sep6.151050.14474@ux1.cso.uiuc.edu> <5057@mit-caf.MIT.EDU> <58@persian.cs.utexas.edu>
Sender: news@awdprime.UUCP
Distribution: na
Organization: IBM AWD, Austin, TX
Lines: 42

In article <58@persian.cs.utexas.edu> garnett@cs.utexas.edu (John William Garnett) writes:
>>[ transcript of bounced mail from Jim Vlcek ]
>><<< 553 foobar.mit.edu Do not communicate with self
>>[...]
>I have received this same message in the past.  My mistake
>was to use only one argument to the Cw macro when it actually
>requires two (or none).  It appears that this may be the problem you
>are experiencing.
>
>I would try "Cw foobar barfoo" or just "Cw".

Just to straighten this up a bit, the above problem was caused by two
macros being defined as null strings, when they should have been left
undefined (i.e., commented-out).  In the sendmail.cf file, there is
a rewrite rule that looks something like:

R$+<@$=w$?E.$=E$.$?F.$=F$.$?G.$=G$.$?H.$=H$.>   $@$1<@LOCAL.D>

whose intent is to see if the address in question is the local machine.
While this is a litle hard to read, the "$?M" contruct is a simple if-then
statement that tests whether the M macro has been defined; if so, it checks
for it in the address, preceded by a dot (".$=M").  So when Jim had the G
and H macros defined as null strings, the rule was checking to see if the
address matched "foobar.mit.edu.." instead of "foobar.mit.edu", and of
course it wasn't matching, and therefore it didn't recognize it as itself,
and it accordingly tried to connect to itself as a remote server.

The w class should specify all of the hostnames that your host can be known
by; likewise, the E, F, G, and H classes should specify all of the domain
parts that your host can be known by.  The "$=w" construct will then match
any of these names, and thereby allow you to receive mail that is addressed
to any of your domain names.  So if you are known as both foobar.mit.edu
and barfoo.mit.edu, then you would need to do:

Cw foobar barfoo

Otherwise, just the "Cw foobar" would be sufficient.

-------------------------------------------------------------------------------
Peter Jeffe   ...uunet!cs.utexas.edu!ibmaus!auschs!sandino.austin.ibm.com!jeffe
        first they want a disclaimer, then they make you pee in a jar,
                   then they come for you in the night