Announcements
09/25/2026
DELIVERY - Diplomatic Post Office (09880) resumes mailing services
Announcements
09/25/2026
INFORMATIONAL - RESOLVED - PostalOne! System – Post-Deployment Issues
Announcements
09/25/2026
INFORMATIONAL - Adjustments to Priority Mail and USPS Ground Advantage Service Expectations for Noncontiguous States and Territories
Announcements
09/25/2026
INFORMATIONAL - Commercial System Releases – October 4, 2026
Announcements
09/25/2026
INFORMATIONAL - Hawaii - Hurricane Nolo - Operations Weather Advisory
Announcements
09/25/2026
INFORMATIONAL - PostalOne! Alert - October 4, 2026
Announcements
09/25/2026
INFORMATIONAL - Eastern Region - Nor’easter - Operations Weather Advisory
Announcements
09/25/2026
DELIVERY - Sycamore Post Office (15364) - Suspended Temporarily
Release Notes
09/25/2026
September 24, 2026 COP Release 2.5.6
Release Notes
09/24/2026
October 4 2026 - PO! and ProgReg - Release Notes
Announcements
09/24/2026
National PCC Week 2026 PCC Voice Challenge #PCCWeek2026
Contact Lists
09/24/2026
CASS™ Certified Products Guide: Residential Delivery Indicator Cycle O - (Expires July 31, 2028)
Contact Lists
09/24/2026
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
09/24/2026
CASS™ Certified Products Guide: M L O C R Mailers/Users Data File Cycle O - (Expires July 31, 2028)
Contact Lists
09/24/2026
CASS™ Certified Products Guide: M L O C R Mailers/Users Cycle O - (Expires July 31, 2028)
Contact Lists
09/24/2026
CASS™ Certified Products Guide: M L O C R Service Bureaus Data File Cycle O - (Expires July 31, 2028)
Contact Lists
09/24/2026
CASS™ Certified Products Guide: M L O C R Service Bureaus Cycle O - (Expires July 31, 2028)
Contact Lists
09/24/2026
CASS™ Certified Products Guide: M L O C R Hardware Manufacturers Data File Cycle O - (Expires July 31, 2028)
Contact Lists
09/24/2026
CASS™ Certified Products Guide: M L O C R Hardware Manufacturers Cycle O - (Expires July 31, 2028)
Contact Lists
09/24/2026
CASS™ Certified Products Guide: Z4CHANGE Data File Cycle O - (Expires July 31, 2028)
Contact Lists
09/24/2026
CASS™ Certified Products Guide: Z4CHANGE Cycle O - (Expires July 31, 2028)
Contact Lists
09/24/2026
CASS™ Certified Products Guide: Vendor/Service Licensees Data File Cycle O - (Expires July 31, 2028)
Contact Lists
09/24/2026
CASS™ Certified Products Guide: Vendor/Service Bureaus Licensees Cycle O - (Expires July 31, 2028)
Contact Lists
09/24/2026
CASS™ Certified Products Guide: DSF2® Licensees Data File Cycle O - (Expires July 31, 2028)
Contact Lists
09/24/2026
DSF2® Licensees Cycle O: Certified Products Guide - (Expires July 31, 2028)
Contact Lists
09/24/2026
DPV® Licensees Data File Cycle O: Certified Products Guide (D) - (Expires July 31, 2028)
Contact Lists
09/24/2026
DPV® Licensees Cycle O: Certified Products Guide - (Expires July 31, 2028)
Contact Lists
09/24/2026
CASS™ Software Manufacturers Data File Cycle O: Certified Products Guide (D) - (Expires July 31, 2028)
Contact Lists
09/24/2026
CASS™ Software Manufacturers Cycle O - (Expires July 31, 2028)
Contact Lists
09/24/2026
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
09/24/2026
Z4 Info File

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

Data Files
09/24/2026
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.

 

Announcements
09/23/2026
DELIVERY - International Suspension of Mail Service - Effective September 25, 2026
Announcements
09/22/2026
Update - Central Processing Region - Louisville, KY Processing and Processing and Distribution Center (P&DC)
Announcements
09/22/2026
DELIVERY - Atlantic Area – Maryland District - Hughesville Post Office (20637) - Temporarily Closed
Announcements
09/22/2026
INFORMATIONAL - Commercial System Releases September 24 & 29, 2026
Contact Lists
09/22/2026
Mailers Technical Advisory Committee (MTAC) Membership Roster and Vacancies
Announcements
09/21/2026
INFORMATIONAL - USPS APIs System Release Notification – September 24, 2026
Data Files
09/21/2026
2027 Labeling List and Mail Direction File Schedule

This is the Labeling Lists production schedule for 2027.

Announcements
09/21/2026
DELIVERY - PostalOne! System - Issue with Finalizing Parcel Mailings and Application of IMpb Noncompliance
Announcements
09/21/2026
DELIVERY - Postal Service Updates for September 2026 S&DC Activations
Announcements
09/21/2026
What is the Postal Customer Council Advisory Committee (PCCAC)?
Announcements
09/21/2026
PROCESSING AND DISTRIBUTION - – Indianapolis, IN Regional Processing and Distribution Center (RPDC) Delays
Announcements
09/21/2026
PROCESSING AND DISTRIBUTION - Amarillo, TX Regional Processing & Distribution Center Activate on September 28, 2026
Contact Lists
09/21/2026
MTAC UG-WG-TT Leadership Roster and Matrix
Data Files
09/21/2026
***Updated - New Areas*** - Area District 5-digit ZIP Codes (AREADIST_ZIP5.TXT)
Data Files
09/21/2026
City/State ZIP Code Weekly Compare
Data Files
09/21/2026
3 Digit ZIP/AISU Office List (AISUREPT.TXT)
Data Files
09/21/2026
AIS Congressional District File (CONG_DIST.TXT)
Data Files
09/21/2026
AIS County Name Table Layout (AISCNTY.TXT)