In Exchange, if you try and move a mailbox that h as a completed move request, you will receive the following error:

To fix this error, you need to clear the move requests, to do so you can run the following command:

  • Get-MoveRequest | Remove-MoveRequest

As you can see above, I did not include the $confirm option, if you have hundreds of move requests to clear you don’t want to type “y” for each one.

After it has cleared the move request you can re-submit your move request and it should go through.

Hope it helps.