Certificate of Mailing — Firm - USPS
about.usps.com › forms › ps3665present the form and mailing at a business mail entry unit (BMEU) or USPS-authorized detached mail unit (DMU). Privately Printed Forms: The Postal Service allows mailers to use USPS-approved privately printed or computer-generated firm sheets that are nearly identical in design elements and color to the USPS-provided PS Form 3665.