Contact Lists
12/31/2025
CASS™ Software Manufacturers Cycle O - (Expires July 31, 2028)
Contact Lists
12/31/2025
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.

Announcements
12/29/2025
DELIVERY - WestPac Area: California 6 District - Wrightwood Post Office and Lytle Post - Resume Operations
User Guides
12/29/2025
USPS APIs Terms and Conditions

ACKNOWLEDGEMENT AND ACCEPTANCE. Read this carefully before registering to use the USPS API services. By utilizing the APIs, you hereby ACCEPT ALL of the terms and conditions of this Agreement. 

Announcements
12/29/2025
INFORMATIONAL: USPS APIs System Deployment - January 10, 2026
Data Files
12/29/2025
Labeling List Changes Effective February 1, 2026

Effective February 1, 2026, the Postal Service™ will revise Labeling List(s) L002, L005, L012, 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 February 1, 2026, effective date through March 31, 2026, expiration date. The changes will be published in the Postal Bulletin, Issue #22694.

Announcements
12/26/2025
DELIVERY - Wrightwood Post Office (92397) - Temporarily Closed
Announcements
12/26/2025
DELIVERY - Lytle Creek Post Office (92358) - Temporarily Closed
Announcements
12/23/2025
INFORMATIONAL - USPS APIs System Maintenance January 14, 2026
Data Files
12/22/2025
12_22_25_PTR2 Release Notes