Okay, this is weird. I am getting the following error when I check my event application logs:
An error occurred during a POP3 transaction to server <mail.server.com [username]>. The error is 1232 (The network location cannot be reached. For information about network troubleshooting, see Windows Help.
I have about 15 other entries in the pop3 connector and they all download/deliver their mail fine. Yes, I've double checked all the details for this account. I even entered the details straight into Outlook alongside the exchange account for this user and the mail downloaded fine (so the details are definitely correct). I've changed the password on the pop3 account. I've tried changing which exchange mailbox the mail is delivered to just for the hell of it. Nothing works. Same error as above.
From some googling I find that this used to happen if a NULL character was found in an email address or if an end of message signal was never reached...but these errors were all fixed in a service pack for SBS2000. I'm using SBS2003 fully updated (including Exchange 2003 SP2). Also apparently some characters in passwords throw off the pop3 connector...changed the password to just regular text (a smiple word) and still the above error.