error #0x800CCC79

[Brian]

On one of my mail boxes mail isn't working; I get the
message:

The message could not be sent because one of the
recipients was rejected by the server. The rejected e-mail
address was '(e-mail address removed)'. Subject 'test',
Account: 'postoffice.worldnet.att.net',
Server: 'mailhost.worldnet.att.net', Protocol: SMTP,
Server Response: '551 not our customer', Port: 25, Secure
(SSL): No, Server Error: 551, Error Number: 0x800CCC79

 

[Jeff Stephenson [MSFT]]

That seems to be saying that the email address to which you're sending is
not valid. You should verify that address.