[comp.mail.sendmail] Funny Sendmail/DNS interaction

rickert@mp.cs.niu.edu (Neil Rickert) (02/06/91)

In article <73973@bu.edu.bu.edu> eap@bu-pub.bu.edu (Eric A Pearce) writes:
>I apologize if this is a lame question.
>
>I had a user who was confused when they sent mail to 
>
>username@bu-bio.bu.edu.    <--- notice period on end
>
>Sendmail accepted this and blew up later with "local config error, hostname
>not recognized as local"
>

 You didn't complete the picture.  I will assume that this problem arose on
the host 'bu-bio.bu.edu' .

 What happened is that, as you suggest, an attempt was probably made to see
if the hostname was 'bu-bio.bu.edu' but because of the added '.' the test
failed and the address was not recognized as local.  Then the nameserver was
consulted which gave an internet address.  Sendmail proceeded to establish
an SMTP connection.  However it discovered it was 'talking to itself' and
gave the error message you indicated.

 The real problems are that:
  1) Addresses ending in a period are technically invalid.

  2) You sendmail configuration could not handle this error.

  What you need is to run the domain through the $[ ... $]  operation
before trying to determine whether it is local.  This will remove the
additional period.  It will also append your domain if an unqualified
address was used, and will resolve CNAMEs (aliases).  The $[ ... $]
operation is a very useful tool for standardizing address formats prior
to recognition, and you should learn to use it effectively.

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