Taping a BRM envelope to a heavy box (like a "box of rocks") is often considered a mail prank or "trolling." While some claim it forces companies to pay high shipping fees, the USPS may treat it as nonmailable or return it to the sender. 🎬 " No Postage Necessary " (2018 Film) I Love No Postage Necessary Sales Pieces | by Ed Swartz
To be valid, the envelope or card must meet strict USPS Postal Explorer standards: No Postage Necessary
The words "BUSINESS REPLY MAIL" must appear in capital letters (at least 3/16 inch high) above the address. Taping a BRM envelope to a heavy box
The permit number, city, and state of the issuing post office must be listed below the legend. Common Misconceptions No Postage Necessary