Announcements
06/12/2026
DELIVERY - South Colton Post Office (13687) - Suspended Temporarily
Announcements
06/12/2026
INFORMATIONAL - USPS Occupancy Trends Product
Announcements
06/12/2026
INFORMATIONAL - USPS Population Mobility Trends Product
Announcements
06/11/2026
INFORMATIONAL - Upcoming USPS.com Maintenance on July 11, 2026
Release Notes
06/11/2026
USPS APIs Release Notes

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

Contact Lists
06/11/2026
CASS™ Certified Products Guide: Residential Delivery Indicator Cycle O - (Expires July 31, 2028)
Contact Lists
06/11/2026
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
06/11/2026
CASS™ Certified Products Guide: M L O C R Mailers/Users Data File Cycle O - (Expires July 31, 2028)
Contact Lists
06/11/2026
CASS™ Certified Products Guide: M L O C R Mailers/Users Cycle O - (Expires July 31, 2028)
Contact Lists
06/11/2026
CASS™ Certified Products Guide: M L O C R Service Bureaus Data File Cycle O - (Expires July 31, 2028)
Contact Lists
06/11/2026
CASS™ Certified Products Guide: M L O C R Service Bureaus Cycle O - (Expires July 31, 2028)
Contact Lists
06/11/2026
CASS™ Certified Products Guide: M L O C R Hardware Manufacturers Data File Cycle O - (Expires July 31, 2028)
Contact Lists
06/11/2026
CASS™ Certified Products Guide: M L O C R Hardware Manufacturers Cycle O - (Expires July 31, 2028)
Contact Lists
06/11/2026
CASS™ Certified Products Guide: Z4CHANGE Data File Cycle O - (Expires July 31, 2028)
Contact Lists
06/11/2026
CASS™ Certified Products Guide: Z4CHANGE Cycle O - (Expires July 31, 2028)
Contact Lists
06/11/2026
CASS™ Certified Products Guide: Vendor/Service Licensees Data File Cycle O - (Expires July 31, 2028)
Contact Lists
06/11/2026
CASS™ Certified Products Guide: Vendor/Service Bureaus Licensees Cycle O - (Expires July 31, 2028)
Contact Lists
06/11/2026
CASS™ Certified Products Guide: DSF2® Licensees Data File Cycle O - (Expires July 31, 2028)
Contact Lists
06/11/2026
DSF2® Licensees Cycle O: Certified Products Guide - (Expires July 31, 2028)
Contact Lists
06/11/2026
DPV® Licensees Data File Cycle O: Certified Products Guide (D) - (Expires July 31, 2028)
Contact Lists
06/11/2026
DPV® Licensees Cycle O: Certified Products Guide - (Expires July 31, 2028)
Contact Lists
06/11/2026
CASS™ Software Manufacturers Data File Cycle O: Certified Products Guide (D) - (Expires July 31, 2028)
Contact Lists
06/11/2026
CASS™ Software Manufacturers Cycle O - (Expires July 31, 2028)
Contact Lists
06/11/2026
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
06/11/2026
Z4 Info File

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

Data Files
06/11/2026
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
06/10/2026
INFORMATIONAL - July Price Change 2026 - Commercial System Releases June 28, 2026
Announcements
06/10/2026
INFORMATIONAL - Mailer ID (MID) Validation for Payments API June 22, 2026
Announcements
06/10/2026
DELIVERY - International Service Resumption Notice effective June 12, 2026
Announcements
06/09/2026
DELIVERY - Lone Rock Post Office (50559) - Suspended Temporarily
Presentations
06/09/2026
Atlantic AIM Presentation - June 3, 2026
Contact Lists
06/09/2026
Atlantic AIM Leadership 2026
Announcements
06/08/2026
INFORMATIONAL - New Mail.dat client for July 2026 Price Change June 28, 2026
Announcements
06/08/2026
INFORMATIONAL - USPS APIs System Release Notification June 10, 2026
Data Files
06/08/2026
***Updated - New Areas*** - Area District 5-digit ZIP Codes (AREADIST_ZIP5.TXT)
Data Files
06/08/2026
City/State ZIP Code Weekly Compare
Data Files
06/08/2026
3 Digit ZIP/AISU Office List (AISUREPT.TXT)
Data Files
06/08/2026
Cumulative Listing of ZIP Codes Covered by the LACS Database

This document provides a cumulative listing of ZIP Codes covered by the LACS database for LACSLink®.

Data Files
06/08/2026
AIS Congressional District File (CONG_DIST.TXT)
Data Files
06/08/2026
AIS County Name Table Layout (AISCNTY.TXT)
Data Files
06/08/2026
AMS County Name Table (COUNTY_NAME_TABLE.TXT)
Contact Lists
06/08/2026
AMS Address Report: AISU Mailing List (ADDRREPT.TXT)
Data Files
06/08/2026
AISU ZIP Code Record and AISU Address Record Descriptions (AISULOUT.TXT)
Data Files
06/08/2026
AISU ZIP Code File (AISUZIPS.TXT)
Data Files
06/08/2026
AISU Contact Information (AISUADDR.TXT)
Data Files
06/08/2026
Area District Finance File Specification (AREA_DIST_LAYOUT.TXT)
Data Files
06/08/2026
Area District Finance File (AREADIST.TXT)
Data Files
06/08/2026
Area/District 3-digit and 5-digit ZIP Code Assignments (AREA_DIST_ZIP.TXT)
Data Files
06/08/2026
Move to Competitive Street Addressing (MTC SA) List

This .txt file contains the MTC SA List.

Announcements
06/06/2026
INFORMATIONAL: USPS APIs System Deployment [CR# TBD] - Saturday, June 27, 2026