I am having an issue with one of my client’s exchange servers. They have one external client that they cannot send any email to but if I get the external client to send a test message, it will be received without any issues. I have confirmed that he is using the same email address as we have. The domain is @iastate.edu
When I send a test message to the external clients email address, it shows up in the outbound exchange queue and never leaves. Eventually, I get the following error;
Error: #550 4.4.7 QUEUE.Expired; message expired ##
If I open the receive log files, I can see that there are no messages showing an attempt to deliver that message.
The folder I was looking in was as follows;
C:\Program Files\Microsoft\Exchange Server\V14\TransportRoles\Logs\ProtocolLog\SmtpSend
Exchange mail flow troubleshooter doesn’t show anything wrong
What can I do to narrow down where the problem may be?