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From: rickert@mp.cs.niu.edu (Neil Rickert)
Newsgroups: comp.unix.admin
Subject: Re: Sendmail won't send back bogus mail to user
Message-ID: <1990Nov1.155152.25989@mp.cs.niu.edu>
Date: 1 Nov 90 15:51:52 GMT
References: <1211@lehi3b15.csee.Lehigh.EDU>
Organization: Northern Illinois University
Lines: 32

In article <1211@lehi3b15.csee.Lehigh.EDU> porphano@hobbes.sfc.lehigh.edu (Paul A. Orphanos) writes:
>Hi folks,
>   I've had this persistent small problem with Sendmail on our system.
>We got the one from Berkeley, and set it up with no problems.
>Everything seems to work fine except for one thing. When a local user
>addresses a message, and mistypes the address (causing a nslookup
>failure), the message just sits in the mail queue, and is not sent

  The behavior that concerns you is actually the correct behavior.

  Sendmail is designed to bounce the mail when the nameserver returns
NXDOMAIN (non-existent domain), but not for a name lookup failure.  A name
lookup failure may be the result of a temporary network problem which makes
access to the nameservers for the destination zone to be unavailable.  It
is appropriate in this case to queue the message and keep trying.

  I believe you will find that the message eventually bounces after two or
three days of trying.

  You may be suffering from a different problem.  Recently there were some
bogus NAMESERVER records around which caused nameservers to indicate failure
for addresses that should have been returned with NXDOMAIN.  Your nameserver
may be suffering from this problem.  If it is, you may need to kill your
nameserver and restart it, for those bogus records had rather long TTL times.
Note that recent bind releases have provided nameservers which do not purge
their cache on restart (kill -HUP), so you will need to actually kill and
restart if you have such a nameserver.
-- 
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  Neil W. Rickert, Computer Science               <rickert@cs.niu.edu>
  Northern Illinois Univ.
  DeKalb, IL 60115.                                  +1-815-753-6940