Media Mail Service - USPS
about.usps.com › notices › not121Upon such inspection, matter not eligible for the Media Mail rate may be assessed at the proper rate and sent to the recipient postage due, or the sender may be contacted for additional postage (DMM 604.8.1). For more information about Media Mail service, please visit www.usps.com or call 1-800-ASK-USPS (1-800-275-8777). Complete explanations ...