Announcements
01/29/2026
INFORMATIONAL - Scheduled Commercial Systems Releases – February 1, 2026
Announcements
01/29/2026
INFORMATIONAL - USPS APIs System Maintenance February 11, 2026
Announcements
01/29/2026
INFORMATIONAL - MID Validation for Payments API
Release Notes
01/29/2026
USPS APIs Release Notes

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

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01/29/2026
CASS™ Certified Products Guide: Residential Delivery Indicator Cycle O - (Expires July 31, 2028)
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01/29/2026
RDI™ Cycle O: Certified Products Guide (D) - (Expires July 31, 2028)

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

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01/29/2026
CASS™ Certified Products Guide: M L O C R Mailers/Users Data File Cycle O - (Expires July 31, 2028)
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01/29/2026
CASS™ Certified Products Guide: M L O C R Mailers/Users Cycle O - (Expires July 31, 2028)
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01/29/2026
CASS™ Certified Products Guide: M L O C R Service Bureaus Data File Cycle O - (Expires July 31, 2028)
Contact Lists
01/29/2026
CASS™ Certified Products Guide: M L O C R Service Bureaus Cycle O - (Expires July 31, 2028)