We’ve been having a nightmare of a time migrating to the new corporate mail system. Everything from missing accounts, to bounced emails. We’ve managed to whittle the issues down, but one kept on coming up. One particular user had issues with receiving emails, and it seemed rather sporadic. When emailing her, 2 out of 3 would bounce, and the third would be delivered fine. This was beginning to cause some headaches, and management wasn’t too happy. After spending several hours working on the issue, her account was recreated, but issues persisted. Then one of the techs that are managing our corporate exchange server recalled an option in Exchange, called the “X500” proxy account. This basically adds another option to the mail account profile, and lets the new account receive mail for the old one. Microsoft has an article on it here. Very handy to know, wish I’d known about it 2 years ago when I was moving mailboxes.