I've got a user who was recently added to AD and Exchange. As fate would have it, she has the same name as someone else. The admin who deleted the old user added the new user the same day. I suspect that instead of creating a new mailbox for the new user, he connected the new user to the old user's mailbox. We began receiving IMCEAEX NDR messages the moment anyone attempted to send her an email.
So I went with my gut and disabled the mailbox and created the user a new mailbox. We continue to receive IMCEAEX NDRs. It's not the Outlook cache on any client. I viewed the LegacyExchangeDN of the new user in ADSIedit and it is different than the one in the IMCEAEX NDRs. I suspect the old user is being referenced in those NDRs.
1. Will it resolve my problem if I change the LegacyExchangeDN?