Updated Mail.dat Tech Specs Guide

The USPS released an updated Mail.dat Technical Guide on January 9, 2023 — Version 4, Release 57.

The technical guide that outlines steps for exchanging electronic data with the PostalOne! system using the Mail.dat file format. The guide is for business mailers who create or use mailing data in the preparation or production of business mail and who also want to conduct business electronically instead of traditional hardcopy forms and processes used in business mail acceptance.

Click to download Mail.dat Technical Guide