We have a 10 user SBS 2008 network with Exchange mailboxes for email. We've added a new user and configured his Outlook profile, using identical settings to other users. His account can send emails but cannot receive emails. Senders get a 550 User Unknown error.
All other existing users mailboxes are working fine. I created another new account to see if the problem occurred again and it did. So I now have two users with mailboxes that cannot receive email. All user settings in SBS and Exchange are the same - only the user names and mailbox sizes are different.
The user is connecting to the SBS server via a VPN.
Many thanks for any advice.