Release Notes
03/27/2026
Release Notes
03/27/2026
Data Files
03/27/2026
Labeling List Changes Effective May 1, 2026

Effective May 1, 2026, the Postal Service™ will revise Labeling List(s) L007, L012, L014, L016, L051, 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 May 1, 2026, effective date through June 30, 2026, expiration date. The changes will be published in the Postal Bulletin, Issue #22700.

Contact Lists
03/26/2026
RDI™ Cycle O: Certified Products Guide (D) - (Expires July 31, 2028)

This document outlines the CASS/MASS certified vendors list for RDI™ Cycle O.

Contact Lists
03/26/2026
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
03/26/2026
Z4 Info File

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

Data Files
03/26/2026
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.