I have a mail server that serves multiple domains. I have 2 users that use a specific domain. User A does not experience any issues when sending and receiving mail. User B can send emails fine and receives emails fine from most external users. However when Sender1 sends an email to UserB , the sender gets a "#550 5.1.1 RESOLVER.ADR.RecipNotFound; not found ##" message. However Sender1 can send to UserA just fine. I suspected that the issue was UserB was not setup correctly in exchange. After verification I determined this was not the issue. I then sent UserB emails from a number of external email addresses outside of our domain (Google, Yahoo, MSN) all of which were delivered, as they should have been. I am now out of guesses as to what the issue could possibly be. Any takers?


  • Have you found a solution for this problem yet? I'm running into the same message when one user gets e-mail from some external senders... – SilverViper Jan 27 '13 at 20:47

Go into Powershell or the console and look at the properties (SMTP adresses) on both particular users.

It seems that one of the users might have gotten a wrong policy so that the correct smtp domain might not be listed on the mailbox.

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