AD/Exchange user account does not show up in EV

One of our Exchange 2003 users has his mailbox and AD account set up correctly. When I use the EV Management console to enable his mailbox it does not show up in the available mailboxes. I look in the list of Exchange mailboxes and his name does not appear there either. The guy clearly has a mailbox and AD account which are working well but somehow EV has not picked it up. Can I correct this manually somehow or do I have to scrap his account and create a new one?

Your assistance would be much appreciated.