Sendmail

Не уходит почта с локальных машин. Стоит Sendmail и IPOP3. Выдает такое сообщение: "The message could not be sent because one of the recipients was rejected by the server. The rejected e-mail address was "www@qqq.net". Subject "wwwww", Account: "mail.sss.org", Server: "mail.sss.org", Protocol: SMTP, Server Response: "551 5.7.1 we do not relay", Port: 25, Secure(SSL): No, Server Error: 551, Error Number: 0x800CCC79"