I'll bet you have not heard this one before. I was attempting to send an email to a potential client. Everything seemed to work well except that it was returned. The problem was that the address was changed somewhere. His name is spelled with a j but somewhere along the line, it was changed to a k and so there was no such person and therefore was returned to me.
#550 5.1.1 RESOLVER.ADR.RecipNotFound; not found ##rfc822;
What could have happened? This is a new one on me.