Exchange Hybrid deployment sending out errors for old dismounted databases

Question

I am fairly new to this organization and have inherited a Hybrid Exchange deployment. I have two on-prem Exchange 2013 CU23 servers with dismounted databases that are throwing errors for the databases being corrupted. These databases, apparently, haven't been mounted since 2017, but yet, it is still trying to mount them and access them. Errors 3154, 231, 2006, 3001, and many more. The question is this, did they misconfigure something when moving to the hybrid deployment? Why would the servers still be trying to mount these databases when our mailboxes all reside on O365? Any help at all would be much appreciated. Thank you

Answer 1

If they are unmountable, consider simply deleting them then re-creating the arbitration mailboxes on a new, clean database when you mount it.
https://learn.microsoft.com/en-us/exchange/architecture/mailbox-servers/recreate-arbitration-mailboxes?view=exchserver-2019

If ALL the user mailboxes are moved to 365, then all you need is those arbitration mailboxess.

Answer 2

Those databases should be mounted:)
Exchange doesnt know your mailboxes are in 365, so I would mount them ( How many?)
This way the arbitration mailboxes can be functional.

If you have more than one database, you can move/verify all the arbitration mailboxes to one DB and remove the other DBs

Get-Mailbox -Arbitration | New-MoveRequest -TargetDatabase "DBtoKeep"

Answer 3

I have the secondary server up and running as well as the arbitration mailboxes. Considering the amount of time since these have been healthy, they have not been syncing connectors. Is there an easy way to update server two with the connectors from server one, or is it just the export/import through powershell? Also, thank you AndyDavid for your help.