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From: sra@LCS.MIT.EDU (Rob Austein)
Newsgroups: comp.protocols.tcp-ip.domains
Subject: Domain names in resource records (was: PTR records ...)
Message-ID: <9101181603.aa02093@mintaka.lcs.mit.edu>
Date: 18 Jan 91 21:03:32 GMT
References: <1991Jan17.210309.15170@mp.cs.niu.edu>
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   Date: 17 Jan 91 21:03:09 GMT
   From: Neil Rickert <rickert@cs.niu.edu>

   ...	  It next tries to send to the second preference.  Before doing so, it
   compares the name with its own host name to be sure it is not sending to
   itself.  Because the name on the MX is the name of the CNAME record, and not
   of the A record, it does not recognize the name as its own.  It therefore
   tries sending to itself, discovers the problem, aborts and bounces the mail.

    I believe the problem is not in sendmail, but in the MX -> CNAME.

Sorry, but this is dead wrong.  There is no technical difficulty
involved in checking both the source and the target of the CNAME.  If
sendmail doesn't do this, sendmail is broken.  TOPS-20 MMAILR got this
right years ago.

--Rob Austein <sra@lcs.mit.edu>