I have a problem with internal mail flow. On one shared mailbox I have this issue, that when email is sent to it, some users don't get it. It's Microsoft Exchange Server 2016.
I did use Test-Mailflow and was logged in over OWA, to confirm this case.
What I have seen is that I have successful Test-Mailflow Result, and mail do arrive at it's destination, but disappear after a second.
Why is this happening I was not able to understand, but what I did found out is when I restart Microsoft Exchange Information Store service, it starts working fine.
But after a day or so, this problem happens again.
Does anyone had similar problem so far?
Here is MessageTrackingLog.
You can see it here log for one particular internal mail which is problematic.
One user which was not reached, is no longer exists.