I am fairly new to administering the Exchange server at my workplace. I am looking to set up a new rule that will remove all emails from a specific sender 20 days from sent date no matter what folder it is placed in by the user. A new phone system is in place that will email end users a .wav file for voice mail and text call notifications. This will, in turn, take up lots of valuable space on the server and we all know how outlook is already used by end users as a storage box as it is. The end users have already been notified that they should save important messages on their workstations or on the shared server because they will be removed after 20 days.In short, I am looking for help setting up this rule. Thanks in advance!

You're looking for http://support.microsoft.com/kb/319188 It's not a rule but is rather a "Recipient Policy"

That is exactly what I needed, Thanks!!!!