To remove messages from shadow queues, run this command from Exchange Powershell:
Get-Queue -Server servername | Where {$_.Identity -like “*Shadow*”} | Get-Message | Remove-message -confirm:$false
This will remove the messages from any Shadow queue without prompting you for confirmation.
Ex-Shell 
Wonderful web site. A lot of useful info here. I’m sending it to a few buddies ans also sharing in delicious. And naturally, thanks for your sweat.
LikeLike