Answer
GMS has compared the protocol MAIL clause and the FROM clause in the message itself. For some reason, the two values (which are usually the same) do not match up so an alert has been generated. GMS saves resources by carrying out this check once per email message (and not for each recipient of the email message).
In this particular case, session Undefined was processing a message from a server at Undefined apparently from Undefined. The protocol MAIL clause is Undefined which was compared with the From: clause in the message which was Undefined.
There are many reasons this may occur. Some common explanations are that
- the message is a delivery status notification (DSN) message;
- the message was generated by a list server or is a mass mailing; or
- there is an error in the sending server.
Message delivery is not affected but a clause is added to the headers of the message indicating the failure to match.
See Also:
- What is DSN?
- How do I contact the owner of a client?
- How do I contact the owner of a remote server?
- What is SMTP Response Code Theory?
Keywords:unexpected sender from mail