Contact Lists
09/03/2026
CASS™ Software Manufacturers Cycle O - (Expires July 31, 2028)
Contact Lists
09/03/2026
CASS™/MASS™ Certified Products Guide - All Sections Data Files Cycle O - (Expires July 31, 2028)

This document contains the certified vendors list for CASS™ and MASS™ products for Cycle O.

Data Files
09/03/2026
Z4 Info File

A downloadable ZIP file containing information related to the Z4 Info File

Data Files
09/03/2026
Early Warning System (EWS002C0.ZIP)

This file is the EWS production file and is updated weekly. This file contains the Early Warning System data file for the CASS™ and MASS™ certification process.

 

Announcements
09/02/2026
INFORMATIONAL - Western Region - Beaumont, TX – Tropical Storm Edouard Impacts
Contact Lists
09/02/2026
Mailers Technical Advisory Committee (MTAC) Membership Roster and Vacancies
Release Notes
09/02/2026
USPS APIs Release Notes

For the latest updates, please review the USPS APIs Release Notes.

Announcements
09/01/2026
INFORMATIONAL - UPDATE - Elevate Your Marketing Strategy with USPS 2027 Mailing Promotions Kickoff Webinar
Data Files
09/01/2026
August 2026 Nixie Volume

This spreadsheet contains the UAA statistics for August 2026.

Error Codes
09/01/2026
Known Issues List 8.27.2026