Did you check the mailbox size on the server? My guess is that the mailbox has been downloaded from the server, and is now sitting on the user's Local hard drive. If the mailbox on the server is empty (or nearly empty), I would go to the machine that has the messages, and ensure that "Use Cached Exchange Mode" is NOT checked. If it IS checked, I would copy all the emails to a new .PST file (better to have a copy in case you fudge something up), and then remove the "Use Cached Exchange Mode" and try to import the mail back into the exchange mailbox. Once that is done, I'd delete the user's outlook profile, and create a new one. Best of luck to you