Run Get-Mailbox -Database “Database Name” –Arbitration command to find all the arbitration mailboxes
If there are some arbitration mailboxes, move them to different databases and then delete the database again
If all above don’t work, you can use ADSIEDIT tool to delete mailbox database:
1. Open Adsiedit.msc
2. Connect to the configuration partition.
3. Expand Configuration-Services-Microsoft Exchange–Administrative Groups-Servers–Information Stores.
4. Delete the appropriate database.
I ran Set-AdServerSettings -ViewEntireForest $True then ran get-mailbox -database db1 -arbitration and all of a sudden I now see a mailbox!!! How annoying.
I moved the arbitraion mailbox to another DB and I was then able to delete the DB.
I was not aware of the Set-AdServerSettings command.
get-mailboxstatistics -database |fl