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From: rickert@mp.cs.niu.edu (Neil Rickert)
Newsgroups: comp.mail.sendmail
Subject: Re: Problem with host sending MX-ed mail to itself
Message-ID: <1991Feb15.192439.31276@mp.cs.niu.edu>
Date: 15 Feb 91 19:24:39 GMT
References: <6166@rex.cs.tulane.edu>
Organization: Northern Illinois University
Lines: 27

In article <6166@rex.cs.tulane.edu> mb@rex.cs.tulane.edu (Mark Benard) writes:
>I am running sendmail 5.61 and just noticed the following problem.
>
>We serve as secondary MX site for several other hosts on campus, so when they
>are down, we get their mail.  But after this host receives such mail, it
>tries to forward it to the final destination.  Since the final destination is
>down, it tries the secondary MX site - itself.  (This results in a 553 error
>to prevent looping.)
>
>Shouldn't my sendmail recognize itself as the secondary MX site and just
>queue the mail until the destination can receive it?  Is this a problem with
>sendmail 5.61 or do I just have a configuration error?

  Absolutely it should.  And the code is there in sendmail to do so.  But you
have to be sure you don't outsmart it.

  'sendmail' compares the hostname on the destination of the MX record with
the value of $w.  You must make sure that $w is the FULLY QUALIFIED DOMAIN
NAME of your host, and that the MX record refers to that name and not to some
alias.  Unfortunately there are many rulesets out there which incorrectly use
$w as the unqualified host name.

-- 
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  Neil W. Rickert, Computer Science               <rickert@cs.niu.edu>
  Northern Illinois Univ.
  DeKalb, IL 60115                                   +1-815-753-6940