---
title: "What is a self-mailer?"
description: "A self-mailer is a folded printed piece that mails without an envelope. USPS rules, costs, and use cases compared to postcards and letters."
canonical: https://trysincerely.com/glossary/self-mailer
last_updated: 2026-09-29
---
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# What is a self-mailer?

> A self-mailer is a folded printed piece that mails without an envelope. USPS rules, costs, and use cases compared to postcards and letters.

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 print formats are 4x6 and 6x9 postcards and letters in the US and Canada. Handwritten 4x6 postcards and letters are genuinely written by hand. 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.

## Related questions

- [Postcard or letter, which should you send?](https://trysincerely.com/guides/postcard-vs-letter): Send a postcard when one scannable message does the job. Send a letter when you need room, formality, or privacy. Decision rules with current format costs.
- [What is dimensional mail?](https://trysincerely.com/glossary/dimensional-mail): Dimensional mail is any piece with physical bulk: a box, tube, or lumpy envelope. The postal service prices it as a parcel, not a letter.
- [What determines direct mail postage rates?](https://trysincerely.com/glossary/postage-rates): Direct mail postage rates depend on mail class, shape, weight, presort depth, and where the mailing enters the USPS network.

---

Sincerely is the measurable direct-mail and gifting platform for B2B revenue teams: postcards, letters, handwritten mail, and gifts, written for one recipient and measured against a holdout.

Contact Sincerely: https://trysincerely.com/contact

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