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I was working on a sendmail server the other day and was really frustrated. Something in this machine somewhere is telling it to treat a domain as if it were locally on the box. The problem is, I can't figure out where this is getting done. It's not in the local-host-names file...there's nothing for it in the HOSTS file, DNS points away from the server...I grep'd for the domain name in the sendmail configuration directory...I got nothing. I was able to fix it last week by pointing unknown users of local domains to another mail server, but it's still bothering me today that I couldn't figure out where the configuration for treating a domain as local in sendmail is.

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up vote 0 down vote accepted

I figured out what was causing it. For some reason, there were multiple PTR records setup and one of them was the domain that was in question. Sendmail is doing a PTR lookup on the hostname and automatically adding everything returned as a local domain

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Did your try RTFM?

sendmail uses the following configuration files:

Filename                    Function
/etc/mail/access            sendmail access database file
/etc/mail/aliases           Mailbox aliases
/etc/mail/local-host-names  Lists of hosts sendmail accepts mail for
/etc/mail/mailer.conf           Mailer program configuration
/etc/mail/mailertable           Mailer delivery table
/etc/mail/           sendmail master configuration file
/etc/mail/virtusertable         Virtual users and domain tables

no more than 10 seconds of STFW

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Did you try to read my comment? I said I grep'd all of /etc/mail for the domain name and it's not there. I looked in every single config file in /etc/mail. Maybe you should try not being such a condescending schmuk. – Will Oct 3 '11 at 13:47
If your local hostnames are listed as names of one of the local IP addresses in your /etc/hosts, then none is needed in /etc/mail/local-host-names. You can see the list of host names which Sendmail considers local by running sendmail in "test mode" and expanding the $=w macro to see what hostnames it has already "discovered" as local: $ echo '$=w' | sendmail -bt – Lazy Badger Oct 3 '11 at 14:01
Forgot to mention (long time away from sendmail) possible Cw option in – Lazy Badger Oct 3 '11 at 14:14

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