postfix looping problem

Hey Hey,

Those of you whom frequent IRC may have noticed me talking quite a bit lately about a couple of webservers. I will be taking over admin responsibilities for these servers in the next week or two. As a bit of a background before I get into the problem. There is currently one server online, I have started work on a second server, which will be going online temporarily so that I can take the primary server offline to update it. After that there will be a primary and a backup server, both identical for services... except that the back-up will also be doing shell hosting.

I'm hoping that when I reinstall the servers this problem will be corrected, however I'm looking for similar experiences or thoughts on why this is occuring. The servers are running postfix to handle their email. Customers can check their mail through either IMAP4 or POP3. They can also use SquirrelMail to check their mail from the web. The problem lies in that occasionally, and seemingly randomly, the mail in the accounts will seem to start looping. An Outlook client can check their email and have everything work perfectly for months, and then one day they'll check their email and get their messages, and the next time they check their email they get the same messages again. The messages keep looping into their inbox, until they can end up with 100s if not 1000s of duplicate emails. I've searched google for hours on this subject, and can't find anything that really explains it. I'm hoping that someone here will provide some sort of insight or solution.

Peace,
HT

A long time back, I read of a similar problem. So long ago, I don't remember where. But, I believe it was a conflict between applications on the server that was causing it. Something to do with stacking if I am remeber right at all. Sorry, I can't be more specific.