A method to allow a mailer to receive postal discounts for mailing at an eligible postal facility a plurality of mail pieces to a plurality of mailing addresses. The method comprises the steps of creating an entry code lookup file containing a plurality of identification codes for each eligible postal facility according to the Destination Delivery Unit (DDU) rate or discounting and a drop ship file containing a plurality of local ZIP codes and carrier routes associated with each eligible postal facility. When a mailer enters the identification code for the eligible postal facility where the mailer drops the mail for mailing, the drop ship file is used to determine whether the mail piece is available for DDU discounts based on the local ZIP code and the carrier route.