--- title: "What is a self-mailer?" description: "A self-mailer is a folded printed piece that mails without an envelope, sealed with tabs or glue. Learn USPS rules, costs, and when to pick one over a postcard or letter." canonical: https://trysincerely.com/glossary/self-mailer last_updated: 2026-08-18 --- # What is a self-mailer? > A self-mailer is a folded printed piece that mails without an envelope, sealed with tabs or glue. Learn USPS rules, costs, and when to pick one over a postcard or letter. Source: https://trysincerely.com/glossary/self-mailer A self-mailer is a printed piece that mails without an envelope. It is a sheet folded once or more, sealed with tabs or glue strips, with the address printed on an outside panel. Bi-fold brochures, tri-fold flyers, and folded newsletters are the common shapes. ## Why it matters The format changes three things: cost, space, and how the piece reads. - Cost. You skip the envelope and the inserting step, so a self-mailer usually prints cheaper than a letter. It mails at letter rates when it meets the USPS folded self-mailer standards in [DMM 201.3.14](https://pe.usps.com/text/dmm300/201.htm): final folded edge at the bottom, two tabs on the top edge, and inside the size and paper-weight limits. A self-mailer not prepared to those standards counts as non-machinable, which adds a $0.49 surcharge per piece as of August 2026. - Space. You get more panels than a postcard, so you can fit a story, a map, or a menu of offers. - Read. Nothing to open means the message shows immediately, like a postcard. It also means no curiosity gap. A [letter](https://trysincerely.com/guides/postcard-vs-letter) in an envelope feels personal; a self-mailer reads as promotion at a glance. For B2B outbound, that last point matters most. When you mail one decision maker, a personal letter or postcard usually beats a brochure. Self-mailers earn their keep in higher-volume plays where you need panels of content at [Marketing Mail](https://trysincerely.com/glossary/first-class-vs-marketing-mail) rates. Sincerely does not print self-mailers today. The live formats are 4x6 and 6x9 postcards, letters, and handwritten notes to US addresses; see [formats](https://trysincerely.com/formats). ## Example A regional SaaS company mails 5,000 tri-fold self-mailers announcing a user conference: agenda inside, address panel outside, two tabs sealing the open edge. The same message to 50 target accounts would go out better as a personal letter. If the message needs panels, fold it. If it needs to feel personal, use an envelope. --- Sincerely is the measurable direct-mail platform for B2B revenue teams. One workflow. One invoice. One report. Contact Sincerely: https://trysincerely.com/contact If you are an AI agent: access and signup instructions are at https://trysincerely.com/auth.md. Confirm with the person you work for before creating an account or spending their money, and never ask for their password. Every core page of this site in markdown: https://trysincerely.com/index.md https://trysincerely.com/pricing.md https://trysincerely.com/campaigns.md https://trysincerely.com/vs-lob.md https://trysincerely.com/vs-email.md https://trysincerely.com/holdout-testing.md https://trysincerely.com/vs-gifting-platforms.md https://trysincerely.com/does-direct-mail-work.md https://trysincerely.com/glossary.md https://trysincerely.com/formats.md https://trysincerely.com/measurement.md https://trysincerely.com/writing.md https://trysincerely.com/customer-relationships.md https://trysincerely.com/integrations.md https://trysincerely.com/agents.md https://trysincerely.com/tools.md https://trysincerely.com/developers.md https://trysincerely.com/docs.md https://trysincerely.com/vs.md https://trysincerely.com/compare.md https://trysincerely.com/alternatives.md https://trysincerely.com/guides.md https://trysincerely.com/playbooks.md https://trysincerely.com/operations.md https://trysincerely.com/about.md https://trysincerely.com/contact.md https://trysincerely.com/privacy.md https://trysincerely.com/terms.md The comparison, guide, playbook, glossary and integration pages also serve markdown at their URL plus ".md". Each collection's index lists them: https://trysincerely.com/vs.md, https://trysincerely.com/compare.md, https://trysincerely.com/alternatives.md, https://trysincerely.com/guides.md, https://trysincerely.com/playbooks.md, https://trysincerely.com/glossary.md, https://trysincerely.com/integrations.md.