A machinable letter generally falls between 3.5 x 5 inches and 6.125 x 11.5 inches and within thickness/weight limits.
Letter
Letter-size mail
Preparation & Production
Definition reviewed 2026-07-24. Plavidian reference, written from the USPS Domestic Mail Manual. Final mail classification, postage, and preparation are confirmed after list processing and production review.
Need this applied to a real job?
Ask the Plavidian Mail Expert™ for an answer grounded in the USPS Domestic Mail Manual, or send us the job and we will confirm the preparation before you print.