AT&T Worldnet.

Individual Users

If you received a Non-Delivery Report (NDR):   If you did not receive a Non-Delivery Report (NDR):
450 Error 550 Error   If you did not receive an NDR

There are several reasons for receiving a Nondelivery Report (NDR) 450 error.

The sending system may be attempting to connect too often. Like most service providers we limit the number of connections any one sender can make.

Connection attempts that are made too frequently in a given period of time will also result in the error message.

Periods of transient heavy traffic on our mail servers can also result in delays and the nondelivery error.

What to do: These are temporary occurrences and should clear up soon. If the sending system does not try to automatically send the message again, ask your correspondent to re-send the message and it should get through.

“550 Error. Blocked for abuse”: This means that your mail was blocked because it was sent by a system that we have reason to think has sent high levels of spam to our customers in the past.

What to do: Ask the administrator of your mail system to contact us through our System Administrators' page and provide the information we need to investigate the problem.

“550 Error. Blocked for status: <unknown sender>”: This error indicates that no identifying information has been entered into the DNS (Domain Name System) for this sending system. The AT&T Worldnet mail system, like many others, does not accept messages from mail systems with no DNS records.

What to do: Ask your system administrator to submit identifying information to the DNS. For more information, your administrator should refer to http://www.faqs.org/rfcs/rfc2317.html In the meantime, you should use a fully registered domain for sending your messages, such as the mail system from an ISP or one of the major free e-mail services.

  • Double check the address you used. Is it still valid?
  • Our spam filter rarely sidelines legitimate messages, but it can happen. Try re-sending.
  • Please note that, at periods of high levels of mail activity, it may take up to six hours for a message to reach a recipient's inbox. It's best to wait at least six hours before concluding that the message will not be delivered.
   

Back to AT&T Mailblock Inquiry Website.