Uninstalling Exchange 2010

 
I'm trying to unsinstall Exchagne 2010 on one of our test server but it is failing because it thinks there is an active mailbox. I had moved a test mailbox to the location and since removed it. However when I attempt to uninstall I get this error below.
Mailbox Role PrerequisitesFailedError:Uninstall cannot continue. Database 'Mailbox Database 2103615544': This mailbox database contains one or more mailboxes or arbitration mailboxes. To get a list of all mailboxes in this database, run the command Get-Mailbox -Database <Database ID>. Toget a list of all arbitration mailboxes in this database, run the command Get-Mailbox -Database <Database ID> -Arbitration. Before you can remove this mailbox database, you must disable, move, or remove user mailboxes and move arbitration mailboxes.

Seems there is some autodiscovery user that need to disable or delete before you can uninstall MBX role.
 
Let see what hc support have any idea.

Run this command first to disable the arbitration mailboxes
Get-Mailbox -Arbitration | Disable-Mailbox -Arbitration -DisableLastArbitrationMailboxAllowed:$true

Thanks superb answer.

It also worked for me .. ;)