Contact Lists
10/09/2025
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.

User Guides
10/09/2025
Provisioning Mail Quality Data with Informed Visibility® Mail Tracking and Reporting

Mail Quality Data (MQD-IV) leverages the Informed Visibility® Mail Tracking & Reporting (IV®-MTR) application to enable mailers to receive uncapped Mail Quality Data. Detailed error data from the Mailer Scorecard is available for Full Service, Move Update, eInduction, and Seamless Acceptance.

Contact Lists
10/09/2025
Mail Service Provider (MSP) - Full-Service Certified Mailers

A Mail Service Provider (MSP) offers a variety of solutions to prepare and present Full-Service presort mailings. For more information regarding Certified MSPs, please follow this link: https://postalpro.usps.com/full-service-cert/fact-sheet

 

Data Files
10/09/2025
Z4 Info File

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

Data Files
10/09/2025
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.

 

Release Notes
10/08/2025
USPS APIs Release Notes

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