If you are running Exchange 2016 coexisting with legacy versions like Exchange 2010 or 2013, you might come across errors logged with regards to MsExchDiscovery. Here is a snippet of the error:
Move the mailbox to the Exchange 2016 database. To do that open up the Exchange Management Shell and run the following command, the easiest being moving all arbitration mailboxes:
- Get-Mailbox -Server <Exchange 2010 Server> -Arbitration | New-MoveRequest -TargetDatabase <Exchange 2016 Server DB>
Wait for it to finish and the error should be gone.
Hope it helps.