When using the mailbox move exchange task, sometimes it’ll leave a "ghost" mailbox in the old mailstore. A mailbox that appears to be disconnected from its user account, but the mailbox has been successfully moved to its new home.

This can be quite annoying and won’t let you clean it away using the purge or mailbox cleanup agent. So how do you get rid of the damn thing?

The quickest and easiest solution I have found is to simply start up the mailbox move exchange task and set it to go back to where you have the now ghostly mailbox. It’ll error, saying that it already exists but the next time you refresh that mailstore, your ghost will have been exorcised away. :)