05/28/2026
05/28/2026
05/28/2026
05/28/2026
05/28/2026
Z4 Info File
A downloadable ZIP file containing information related to the Z4 Info File
05/28/2026
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.
05/27/2026
05/27/2026
05/27/2026
05/27/2026
Labeling List Changes Effective July 1, 2026
Effective July 1, 2026, the Postal Service™ will revise Labeling List(s) L001, L007, L009, L012, L016, L201, and L606 to reflect changes in mail processing operations. Mailers are expected to label according to these revised lists for mailings inducted on or after the July 1, 2026, effective date through August 31, 2026, expiration date. The changes will be published in the Postal Bulletin, Issue #22704.
05/27/2026
05/27/2026
05/27/2026
USPS APIs Release Notes
For the latest updates, please review the USPS APIs Release Notes.
05/26/2026
05/26/2026
05/26/2026
05/26/2026
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
05/26/2026
05/26/2026
05/26/2026
05/26/2026
05/26/2026
05/26/2026
05/26/2026
05/26/2026
05/26/2026
05/26/2026
05/26/2026
05/26/2026
Move to Competitive Street Addressing (MTC SA) List
This .txt file contains the MTC SA List.
05/23/2026
05/22/2026
05/21/2026
05/21/2026
05/21/2026
05/21/2026
RDI™ Cycle O: Certified Products Guide (D) - (Expires July 31, 2028)
This document outlines the CASS/MASS certified vendors list for RDI™ Cycle O.
05/21/2026
05/21/2026
05/21/2026
05/21/2026
05/21/2026
05/21/2026
05/21/2026
05/21/2026
05/21/2026
05/21/2026
05/21/2026
05/21/2026
05/21/2026
05/21/2026