Error Message Summary
| Error Code/Message |
Explanation |
What to do |
| 421-failure in DNS look-up. |
We couldn't find information from the DNS of the sending system. Like most mail services, we do not accept messages from senders lacking correct DNS information. | The system administrator should consult http://www.faqs.org/rfcs/rfc1035.html. |
| 450 busy--Please try again later |
The sending system has requested more resources than are available at the moment. |
The sending system should re-try. |
| 521 <0.0.0.0> is blocked |
The sending system has been identified as a source of spam. |
Please see http://www.att.net/general-info/bls_info/521.html for more infomation. |
| 550 [suspend] Mailbox currently suspended--Please contact correspondent directly. |
The account of the BellSouth customer is suspended. |
Contact the customer directly. |
| 550 [permfail] bellsouth.net requires valid sender domain |
We were unable to verify the identity of the sending system. |
Administrator of sending system should enter correct information in DNS (domain name system) |
| 550 unauthorized interface for <0.0.0.0.> |
The sending system is not recognized as a valid source of e-mail. |
Correspondents should use registered mail systems provided by a major ISP or hosting service. |
| 550 <0.0.0.0.> blocked by ldap:ou=rblmx, dc=bellsouth, dc=net |
The sending system exhibited behavior associated with spammers and was blocked. |
After taking steps to mitigate their spam or virus problems, the adminstrators of affected systems can send unblock requests from http://www.att.net/general-info/bls_info/block_admin.html |
Back to AT&T Mailblock Inquiry Website.
