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List:       sendmail
Subject:    Can't stop sendmail from using DNS
From:       "Felix E. Klee" <felix.klee () inka ! de>
Date:       2004-10-29 23:50:25
Message-ID: 1041030000.~INN-FVBa00150.comp-news () dl ! ac ! uk
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Hi,

I'm using sendmail 8.12.10 under Slackware 9.1 which - for testing - I
commonly start as follows.

    /usr/sbin/sendmail -L sm-mtaQQQ -bD -q25m -v

The domain name of my machine is ibm550.klee.  Some configuration files
possibly of interest are available online [1].

Now, the Problem:

When the domain server in the file /etc/resolv.conf is not reachable,
then I get a delay of, I guess, somewhere between 10 and 30 seconds
duration after submitting the command below.  The problem doesn't happen
when the domain name localhost (127.0.0.1) is used instead of
ibm550.klee (192.168.0.5).

MAIL FROM: <felix@ibm550.klee>

When I empty /etc/resolv.conf, or when I put name servers in it that are
well reachable, then the problem goes away.

To avoid DNS queries, for testing, I made sure that the hosts line in
the file /etc/nsswitch.conf only contains the term "files", i.e. not the
term "dns".  But this doesn't solve the problem.

Something else that may be of interest: For making changes in
/etc/resolv.conf affect the delay, I need to restart the sendmail
deamon.  Does sendmail cache the contents of /etc/resolv.conf?

Any ideas how to avoid the delay?  What else could I try?

Felix

[1] http://sites.inka.de/klee/sendmail/post1/config.mc
    http://sites.inka.de/klee/sendmail/post1/local-host-names
    http://sites.inka.de/klee/sendmail/post1/nsswitch.conf
    http://sites.inka.de/klee/sendmail/post1/resolv.conf
    http://sites.inka.de/klee/sendmail/post1/hosts


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