Not exactly sure if this is called an attack but I don't know how else to phrase the question.
Here is the problem. We have a live Exchange Server that is getting huge amounts of NDRs from emails being sent that we are sure are not from the server. What I assume is happening is some company is sending out SPAM from an email address at our domain firstname.lastname@example.org. Seeing as we are not blacklisted I would assume that these emails are not coming from our domain but rather from one of these for hire compaines outside the US. Since the emails are going to bad email adresses and/or are being rejected as SPAM we are getting the NDRs from these bounces. It's a problem because we are getting nearly 100,000 of them! How do we deal with this issue?