Our VM-based listserv/lmail has been running successfully for several
months, but this weekend, posters began to get back the following
bounce message.  It doesn't appear that anything has changed on our
tcp/ip, smtp, lmail, or listserv servers.  The mail router/firewall
was upgraded, but appears to be functioning correctly.

I'd like to figure out if the key to the error is the "MX records will
cause loop" or the "User unknown" message.  I've never understood the
MX loop issue.  Perhaps one of the gurus here can enlighten me.

Here's the bounce message that comes back from the firewall/router:

Subject: Returned mail: User unknown
   ----- Transcript of session follows -----
While talking to lmail.vm.timken.com:
>>> RCPT To:<[log in to unmask]>
<<< 550 Cannot accept mail for this host; MX records will cause loop.
550 listserv@lmail.timken.com... User unknown

   ----- Recipients of this delivery -----
Bounced, cannot deliver:
   [log in to unmask]
Sent successfully:
   <[log in to unmask]>

   ----- Unsent message follows -----
Received: from ctn.vm.timken.com by gateway.timken.com with SMTP id AA05863
  (InterLock SMTP Gateway 3.0 for <[log in to unmask]>);
  Mon, 27 Jan 1997 07:41:27 -0500
Received: from CTNVM103 by ctn.vm.timken.com (IBM VM SMTP V2R3)
   with BSMTP id 1046; Mon, 27 Jan 97 07:41:15 EST
Received: by CTNVM103 RSCS Interchange 1.0.000 id 7550 (NOTE)
          for <listserv@internet>; Mon, 27 Jan 97 07:41:15 -0500
Date:  Mon, 27 Jan 97 07:41:04 -0500
From  "Terry A Moore" <[log in to unmask]>
X-Sender-Data: Sr. I/S Technical Specialist
               The Timken Company, Canton, Ohio
To: <[log in to unmask]>

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