Mail.dat is necessary to submit presort paperwork to the USPS electronically and will be mandatory in order to be considered a Full Service Intelligent Mail Barcode participant.

Mail.dat is a data formatting standard for communicating information about a specific mailing, including data at the segment, pallet, sack or tray, and package levels. It can be used for logistics planning, mail assembly, production and postal payment acceptance.

Send and receive statistical information about mailings without translating the proprietary formatting specifications of various software vendors.

ASCII fixed-format ("flat") files, a perfect medium for communicating complete information describing a complex mailing which can easily be imported into any relational database management system or used as-is by in-house software.