I got a call this afternoon saying that email delivery for an Exchange mailbox had dried up, not even 24 hours after I had changed the POP3 connector to download email from our new email domain.

The Message Tracking Center had the verdict: dozens of emails were getting moved to Exchange's Cateogrizer and going no further.

Long story short, the problem began when I set the primary email (and therefore the reply-from email) to one of the addresses from the new email domain. As long as the primary email adress for the user's mailbox was set to this new domain, emails sent to the external domain and picked up by the POP3 Connector would get stuck in the Categorizer. Changing the primary email to an internal email address prevented this from happening. I could have stopped there, but then every reply to external email would have had the internal email tatooed in the reply-from address, making replies to the reply impossible.

Having done a set-it-and-forget-it with Exchange about 10 months ago, I had forgotten to add the new email domain to our Default Recipient Policy. As long as it wasn't there, using the new domain as part of a user's primary email account would effectively stop Exchange from routing any email to it, or at least the email that was addressed to it, even if the primary email and the send-to on the email were an exact match. Using the new email domain in a primary email address just wrecked everything.

So to come around to the point, be sure to add your new email domain name to the Default Recipient Policy before configuring user accounts with their new email addresses.

Of course, if we were keeping the old email domain (which was already in the Recipient Policy from 10 months ago) I might never had changed the primary email address and would never have realized that there was a policy problem because email routing will work if an invalid email domain name is NOT the primary email address.

Phew, glad I got that off my chest. This is probably total spaghetti to anyone desperate enough to find my blog. Be sure to search Google for "exchange add recipient policy pop3 connector" and you'll get all the worthwhile steps that I'm not going to bother to repeat here.

Tags: exchange, pop3, windows, small business server 2003