Release Notes
07/08/2026
USPS APIs Release Notes

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

Release Notes
06/27/2026
PTR2 Release Notes_DD_06_27_26
Announcements
06/26/2026
PROCESSING & DISTRIBUTION: USPS Launches Three Regional Processing & Distribution Centers (RPDCs) on June 29, 2026
Error Codes
06/25/2026
Known Issues List 6.25.2026
Contact Lists
06/25/2026
CASS™ Certified Products Guide: Residential Delivery Indicator Cycle O - (Expires July 31, 2028)
Contact Lists
06/25/2026
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
06/25/2026
CASS™ Certified Products Guide: M L O C R Mailers/Users Data File Cycle O - (Expires July 31, 2028)
Contact Lists
06/25/2026
CASS™ Certified Products Guide: M L O C R Mailers/Users Cycle O - (Expires July 31, 2028)
Contact Lists
06/25/2026
CASS™ Certified Products Guide: M L O C R Service Bureaus Data File Cycle O - (Expires July 31, 2028)
Contact Lists
06/25/2026
CASS™ Certified Products Guide: M L O C R Service Bureaus Cycle O - (Expires July 31, 2028)
Contact Lists
06/25/2026
CASS™ Certified Products Guide: M L O C R Hardware Manufacturers Data File Cycle O - (Expires July 31, 2028)
Contact Lists
06/25/2026
CASS™ Certified Products Guide: M L O C R Hardware Manufacturers Cycle O - (Expires July 31, 2028)
Contact Lists
06/25/2026
CASS™ Certified Products Guide: Z4CHANGE Data File Cycle O - (Expires July 31, 2028)
Contact Lists
06/25/2026
CASS™ Certified Products Guide: Z4CHANGE Cycle O - (Expires July 31, 2028)
Contact Lists
06/25/2026
CASS™ Certified Products Guide: Vendor/Service Licensees Data File Cycle O - (Expires July 31, 2028)
Contact Lists
06/25/2026
CASS™ Certified Products Guide: Vendor/Service Bureaus Licensees Cycle O - (Expires July 31, 2028)
Contact Lists
06/25/2026
CASS™ Certified Products Guide: DSF2® Licensees Data File Cycle O - (Expires July 31, 2028)
Contact Lists
06/25/2026
DSF2® Licensees Cycle O: Certified Products Guide - (Expires July 31, 2028)
Contact Lists
06/25/2026
DPV® Licensees Data File Cycle O: Certified Products Guide (D) - (Expires July 31, 2028)
Contact Lists
06/25/2026
DPV® Licensees Cycle O: Certified Products Guide - (Expires July 31, 2028)
Contact Lists
06/25/2026
CASS™ Software Manufacturers Data File Cycle O: Certified Products Guide (D) - (Expires July 31, 2028)
Contact Lists
06/25/2026
CASS™ Software Manufacturers Cycle O - (Expires July 31, 2028)
Contact Lists
06/25/2026
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.

Release Notes
06/25/2026
Informed Visibility® Mail Tracking & Reporting (IV®-MTR) Release Notes

These release notes summarize new features and enhancements implemented in deployments to the IV-MTR application.

Data Files
06/25/2026
Z4 Info File

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