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Native macOS · OpenPGP + S/MIME · privacy by design

Matou

A native macOS email client built around privacy: IMAP and SMTP, OpenPGP and S/MIME, local storage, and an optional bridge to existing GnuPG keys.

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Matou

The need

Bring encrypted email into a native Mac workflow without weakening the App Sandbox or asking people to abandon their existing keys.

What we built

A SwiftUI client backed by Core Data and SwiftNIO, with built-in OpenPGP and S/MIME plus an optional signed connector to local GnuPG.

Today

One Mac app for everyday IMAP/SMTP mail and end-to-end encryption, with no Matou mail relay.

Visit matou.app

Matou

Matou is a native email client for people who want encrypted mail without giving up the speed and conventions of a real Mac app.

The goal

Secure email often comes with a fragmented workflow: one app for mail, another for keys, and security controls hidden behind technical settings.

We set out to bring ordinary IMAP and SMTP accounts, OpenPGP, and S/MIME into one coherent interface. Reading, writing, signing, encrypting, and verifying should feel like parts of the same action—not separate tools bolted together.

Native from the first window

Matou is built in SwiftUI around a three-column mailbox, separate compose windows, native menus, keyboard shortcuts, system notifications, and light and dark appearances.

The mail layer uses SwiftNIO and a local SwiftMail package for IMAP and SMTP, including TLS, OAuth where configured, connection recovery, and IMAP IDLE. Core Data keeps mail, folders, conversations, drafts, rules, and contacts available to the native interface.

Encryption inside the workflow

OpenPGP supports inline messages and PGP/MIME, with signing, encryption, decryption, verification, Autocrypt, WKD, and keyserver discovery. Matou can manage keys in its own encrypted local vault.

S/MIME uses Apple’s Security framework and macOS Keychain for certificates and private identities. Encryption and signature status appear directly in the message and compose views, where people need them.

A deliberate security boundary

The main app stays inside the macOS App Sandbox. Credentials and private-key material live in Keychain, while sensitive draft and outbox attachment files are protected with AES-GCM. Matou connects directly to the configured mail providers; messages do not pass through a Matou relay.

Existing GnuPG installations sit outside the sandbox by design. For people who use a ~/.gnupg keyring, gpg-agent, a smart card, or a YubiKey, we built a separately distributed GPG Connector. The two signed apps communicate through an authenticated, versioned XPC boundary. The connector is optional: the embedded OpenPGP engine remains a complete path on its own.

The result

Matou brings daily mail and serious cryptography into one native product, without disguising the trust boundaries underneath it. The app is currently in development for macOS 14 and later.

Follow its release at matou.app.

More work

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