I had a problem with a user’s email account when he was trying to reply to emails it would not let him unless he retyped there email address. some times it would work fine. Reinstalled office but that did not help.
We then exported all his mail into a pst file and removed his exchange 2010 mail box and recreated a new one , reimported his mail all in his side was fine.
But now when an internal user trys to send him and email it bounces. If you look at the email address it looks normal but when you click on it this is what it has.