Contact Lists
08/14/2025
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
08/14/2025
Z4 Info File

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

Data Files
08/14/2025
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
08/13/2025
DELIVERY - Atlantic Area – Connecticut District Morris Post Office (06763) - Temporarily Closed
Announcements
08/13/2025
INFORMATIONAL - USPS APIs System Maintenance August 13, 2025
Contact Lists
08/13/2025
Business Acceptance Solutions & Major Mailer Support Directory

This document provides a contact list for Business Acceptance Solutions (formerly Business Mailer Support) & Major Mailer Support

 

Release Notes
08/12/2025
USPS APIs Release Notes

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

Announcements
08/11/2025
DELIVERY - WestPac Area - CO-WY District Dinosaur, Meeker, and Rangely Post Offices Resume Operations
Announcements
08/11/2025
INFORMATIONAL - Eleven New SDC's in September and October 2025
Announcements
08/11/2025
INFORMATIONAL - Labor Day Holiday 2025