Fail to clean up the source mailbox after the mailbox move (Exchange 2010). I was running out of hard drive space on the virtual Hard drives that contained the Exchange databases. The easy solution would be to increase the size which I end up doing any ways. But I found this issue, It so happens that after I moved the mailboxes to a different database from the Exchange Management control neither the Available New Mailbox Space was increasing nor was I recuperating the hard drive space lost. The message I was receiving after the transfer was “ Warning: Failed to clean up the source mailbox after the move. Error details : Mapi Exception Unexpected Mailbox State: Unable to delete mailbox” In investigating the issue, I found out that I had more studs lingering from previous moves.