Hi, This doesnt do exactly what you are asking but I have found it to be really good… when users delete important emails by accident or maliciously!!!
see this tech note http://support.microsoft.com/?id=178630
This enables you to add a reg key to the server which will allow you to recover emails from any folder in the users mailbox… so long as you have set the messages to be deleted after x number of days.
By default the users can recover their deleted items but after adding the reg entry you will be able to recover any item even if they bypass the deleted items by pressing shift when they delete the item.