Whenever a mailbox is moved in Exchange environment, it creates a move mailbox request entry to track the movement progress. This request will be set to completed once the movement is completed. However, this entry will not be deleted unless the Exchange admin deletes manually. If not done, when the same mailbox move is attempted, it will fail saying another request is in queue. So it is good to delete the completed/failed requests.There is no harm in removing these completed/failed requests.
To view the list of move requests in completed state, try the below command from exchange shell.
Get-MoveRequest | ? {$_.Status -eq "Completed" }
If you want to view the pending requests of a particular account, try the below. Here I am querying for testuser2 mailbox.
Get-MoveRequest -Identity testuser2
Use the below command to clear all completed move requests at single go.
Get-MoveRequest | Remove-MoveRequest -Confirm:$false
Use below command to clear move requests of a given mailbox
Get-MoveRequest -Identity test2 | Remove-MoveRequest -Confirm:$false
All these commands should be executed from Exchange Management Shell