We have users that don't have a mailbox but have an account in AD. They use a shared mailbox that they access via OWA by going to the direct URL of https://mail.domain.com/exchange/username. This works well. Now with Exchange 2010, I can't get it to work unless I make a mailbox for each user, then the direct url works and they can get in. Did something change from 2003 that requires users to have their own mailboxes in order to open other mailboxes?