I have a client that is running SBS2003 with Exchange 2003 sp2. The client is attempting to eliminate employee abuse of email and wants to restrict receipt of external email only from customers. My intuition leads me to create mail enabled contact for each of the customer’s addresses. Then in the “Exchange General” tab of the AD user properties dialog box, select “Delivery Restrictions” select… “Only from:” and add the mail enabled contact to the list. Will this work?