We have just started using EOP for our on-prem Exchange 2013 system.
Most mail is flowing nicely. We have a few outside customers that the mail isn't getting delivered to users mailboxes.
I am looking at the message tracking logs for the on-prem Exchange server in powershell. I see the eventid FAIL and source SMTP. How do I get more information as to why it is failing? I need to get this working and am not sure how. As much detail as possible would be very much appreciated.
Thanks.