Effective January 18, 2026, the Postal Service™ will revise Mailing Standards of the United States Postal Service, Domestic Mail Manual (DMM®), in various sections, to reflect the Postal Service implementing shape-based labeling lists for sectional center facility letters, flats, and parcels. Labeling lists L005, L016, and L051 will be used for letters, flats, and parcels, respectively.
Although these revisions will be published in the DMM January 18, 2026, the labeling list changes are effective February 1, 2026.
A detailed article containing the complete list of the DMM revisions will be available via Postal Explorer® at pe.usps.com.
The Postal Service will incorporate these revisions into the next edition of the online DMM, which is available on Postal Explorer at pe.usps.com.
— Product Classification,
Product Solutions, 1-8-26
