Internally, regardless if we reply to an email or generate a new one, no one can email this one user. However, if we email from the outside, it comes in ok. In the NDR, there is a line that looks weird: IMCEAEX-_O=domain_OU=First+20Administrative+20Group_cn=Recipients_cn=mike+2Edreem@domain.tld #550 5.1.1 RESOLVER.ADR.ExRecipNotFound; not found ## What is interesting is that first, his name is Michael not Mike. Nowhere can I see that it is Mike, but yet, this took the name, made it smaller and added the +2E thing beside it. Does not make sense. Where did it get that from? Any ideas would be appreciated. Thanks.

Forget it, this was self induced. After I posted it, I got off the phone with him, and he admitted to seeing a problem with his legacy x500 name and so he 'fixed' it. Yeah, he fixed it alright. Sorry to have bugged you all with this.