First thing is to reset your password and secret question/answer. Next, I would try setting up a filter to automatically move the messages to a separate folder (or the Trash).
I would let that work for a few days, then turn it off so you don't miss any legitimate Delivery Failure notifications.
-- If a forum member gives an answer you like, give them the Kudos they deserve. If a member gives you the answer to your question, mark the answer as Accepted Solution so others can see the solution to the problem.