Why is some mail returned with the error "possible forged address"?

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Some mail that I send gets returned to me with an error indicating that it contained a possible forged address. I know it is valid so why is this happening?


Some servers do not respond to RFC compliant commands in an RFC compliant way. In this case, the Delivery Status Notification that was set to inform the sender if there was a failure at the server was not being understood by the remote server which was responding with "unknown or illegal alias" to the RCPT clause in the protocol transaction.

You can spot Delivery Status Notifications in your logs by looking for RCPT clauses like this:

SMTP commands such as Delivery Status Notifications are only ever sent by NTMail if the receiving server indicates that they understand them in the response to the EHLO command. In this case the remote server indicates it understands Delivery Status Notifications but in fact it does not.

In order to send mail to a server which is not compliant with RFC 1891 (delivery status notifications), you can disable them in NTMail at Outgoing > ESMTP by simply deselecting "Allow Delivery Status Notification"

For more information on the RFC governing SMTP extensions such as notify, please visit

See Also:

Keywords:exchange failed mail forged address

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