Many duplicate emails received for same user(s)...?

Hey,
Was wondering if anyone had any knowledge on how to contol numerous identical emails on an RH9/Linux box? Here's the dilemma...
Seems while we can host more than one domain under the /mail/etc/local-host-names file, (ie.. domain1.com, domain2.com, domain3.com) we receive 3 identical emails each time mail is sent to ONLY ONE of the domain email accounts (ie.. mtsal@domain1.com). Well, If you send me an (one) email to mtsal@domain1.com, I receive three (3) emails all the same to the same mtsal@domain1.com, mtsal@domain1.com, mtsal@domain1.com account. Anyone know where/which file needs to be tweaked to make Sendmail realize I'm not a triplet?
We're using Microsoft Outlook for mail clients in the office. (Sorry for just cursing out the M word) Thanks.

mtsal

First of all, you need to know that sendmail doesn't really work like that. The local-host-names file doesn't really control multiple domains in the true sense of the phrase. Its only task is to control which domain names that mails are accepted for. However, the domains aren't segregated in any way, just by using that file.

That being said, it's still very strange that you receive multiple mails. Could you send yourself a mail and then post the relevant entries from /var/log/maillog, please?