I migrated all mailboxes from exchange 2010 to exchange 2013. I want to remove the exchange 2010 server but get an error about having arbitration mailboxes. Do I have to move the arbitatration mailboxes to the exchange 2013 server? When I run the arbitration command on the exchange 2013 I see two mailboxes system mailbox and a migration mailbox. After removing the exchange 2010 there isn't any other exchange 2010 server so there doesn't need to be any coexistance between the two version.