550 5.0.0 User Unknown?
Posted on 2009-02-16
One of my customers is using SBS 2003 with exchange, when I send an e-mail, the mail is immediately rejected with the error: The following recipient(s) could not be reached: 550 5.0.0 User Unknown. If I send via Hotmail however, the message is delivered? I also get a different problem from another customer who is also using SBS 2003 with exchange. I can e-mail them, but if they try to e-mail me they get: The following recipient(s) could not be reached:550 5.7.1 Unable to relay? For your additional info, I'm using outlook 2003 via a pop3 account. All help greatfully recieved...