Scenario: Currently a mailbox move has been stuck ‘in progress’. The database it was moving to is now down or cannot be accessed. You cannot remove a move request for a mailbox. Running the Remove-moverequest with the -moverequestqueue and -mailboxguid parameters did not work either as suggested by other articles.
Solution: In ADSI Edit (Default Naming Context mode), locate the user account and right click for properties. Clear the two attributes associated with that user account: msExchMailboxMoveFlag & msExchMailboxMoveStatus