Flectar Mail

Email, made fast again

Built from the ground up for speed. Flectar Mail delivers native performance, instant startup, and as little as 20 MB of RAM.

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Flectar Mail is a lightweight, native home for your email, calendars, and contacts. It is engineered to open instantly, stay responsive, and use a fraction of the memory of a typical web-based mail client.

Why Flectar Mail?

• Fast from the first click. A native interface and local-first data path get you to your inbox without waiting on a browser runtime.
• As little as 20 MB of RAM. Flectar Mail is deliberately designed to keep memory use low, even with a full-featured inbox at your fingertips.
• Everything in one place. Move between mail, calendars, and contacts without stitching together separate apps.
• Offline by design. Your mailbox and calendar are stored locally, so your synced data remains useful without a connection.
• Works with your accounts. Connect Gmail, Outlook and Microsoft 365, or standards-based IMAP/SMTP, JMAP, and CalDAV services.
• Privacy-conscious defaults. Remote images are blocked until you allow them, helping prevent tracking pixels from reporting when you read a message.
• Security by architecture. Email content is never opened in a WebView. Flectar Mail renders HTML and CSS through its own Rust-native pipeline, does not execute email scripts, and blocks remote images by default. This avoids the embedded-browser attack surface by design.
• An experimental Rust renderer. Building an email renderer without a browser engine is new territory. Rendering issues are expected, especially in complex messages, while compatibility continues to improve.
• Made for every screen. Spacious and minimal desktop layouts share the same experience as the touch-friendly compact interface.
• Native and open source. Built from the ground up with Rust. It is not a browser wrapped in a window, and it is released under the AGPLv3.

Files and attachments

Browse JMAP/WebDAV storage, search mail attachments, keep files offline, and preview PDFs, images and text.

Account signatures and OpenPGP

Settings → Accounts → Signatures & OpenPGP provides named signatures, separate new-message and reply defaults, and a composer signature selector. Desktop OpenPGP/MIME signing and encryption use installed GnuPG 2.x with pinentry for private-key passphrases. Required encryption blocks delivery when recipient keys are missing or invalid; protected drafts remain local until Send.

S/MIME and mobile OpenPGP are not currently supported.

Experimental HTML rendering

[!WARNING] HTML email rendering is currently the most experimental part of Flectar Mail. Some messages, especially those with complex or unusual markup and CSS, may not render correctly yet.

To keep the client fully native and memory usage around 20 MB, Flectar Mail renders email HTML with Blitz, a Rust HTML/CSS renderer from the Dioxus team, instead of embedding a browser or WebView.

As far as we know, Flectar Mail is one of the first projects using Blitz for arbitrary, real-world email HTML. Email markup contains plenty of unusual HTML and CSS, so this pushes the renderer into demanding territory. We currently carry several patches on top of Blitz and hope to upstream as much of that work as possible over time.

If you find an email that renders incorrectly, please report it. This approach is still experimental, but it is also a major reason Flectar Mail can remain so lightweight compared with WebView-based clients built with frameworks such as Tauri or Wails.

Make it yours

Choose the workspace that fits the way you handle email. Keep the detailed three-pane layout, switch to a streamlined minimal view, choose a light or dark theme, select a built-in color palette or create a custom one, and show or hide sender avatars.

The full workspace keeps your folders, message list, and selected email visible together. The minimal layout reduces visual noise and gives each part of your inbox more room when you need it.

Light

Full workspace	Minimal workspace

Dark

Full workspace	Minimal workspace

Color palettes

Teal	Green	Purple	Custom

Calendar, contacts, and files

Calendar	Contacts	Files (WebDAV/JMAP)

Made for smaller screens

The compact interface keeps the important actions within reach while giving messages, events, and contacts the full screen when they need it.

Light	Dark

Get Flectar Mail

Flectar Mail is currently in development and is not yet stable.

[!NOTE] We are waiting for Google and Microsoft to complete OAuth app verification before the first stable release with Gmail, Outlook, and Microsoft 365 OAuth configured by default. Earlier GitHub prereleases are intended for testers using their own OAuth registrations or IMAP/JMAP accounts.

Builds without OAuth app keys keep Gmail and Outlook sign-in disabled. Use the Sign-in settings cog on the welcome screen to save your own Google or Microsoft app registration, or connect an IMAP/JMAP account. Custom keys are shared with Settings and take precedence over bundled keys; clearing a custom client ID restores the defaults when available. Each provider enables separately once its configuration is saved.

When preview builds are published, download them from GitHub Releases and look for the Pre-release badge:

• Linux x64: AppImage, Debian/Ubuntu .deb, Fedora .rpm, or a sideloaded Flatpak preview bundle
• Windows x64: Setup .exe or portable ZIP
• macOS Apple silicon (macOS 14+): DMG or application ZIP
• Android arm64 (Android 8.0+): Experimental test APK in prereleases

Windows previews are unsigned; macOS previews are ad-hoc signed and not notarized, so operating-system security prompts are expected. Install updates manually.

The Flatpak preview is provided as a standalone test bundle. It is not yet a Flathub package and therefore does not receive automatic Flathub updates. Its close-to-tray option is disabled until the tray backend can use a sandbox-safe D-Bus name.

Install the downloaded Linux package with either sudo dnf install ./flectar-mail-<version>-linux-x64.rpm or flatpak install --user ./flectar-mail-<version>-linux-x64.flatpak. Launch the Flatpak with flatpak run com.flectar.mail.

Each GitHub release includes SHA256SUMS and signed build-provenance attestations. With GitHub CLI installed, verify a download with gh attestation verify <download> --repo flectar/mail.

Android APK updates require the same signing key; builds without a persistent test key may require uninstalling the previous app, which deletes local app data.

You can also build Flectar Mail from source with the Rust toolchain:

cargo run --bin flectar-mail

Linux desktop OAuth uses the system browser through the desktop portal and stores refresh credentials through the freedesktop Secret Service. A normal desktop session therefore needs an xdg-desktop-portal backend and a Secret Service provider such as GNOME Keyring. Release builds stop before opening the OAuth page when secure credential storage is unavailable, so an authorization grant can never be completed without a safe place to persist it.

Podman and Docker development shells commonly have neither the host session D-Bus nor the host browser's loopback network. Debug builds support that setup with a clearly marked, owner-only development credential file and an accordion for pasting the final loopback callback URL. The file backend is excluded from release builds.

Open source, for everyone

Flectar Mail is one open-source application. There is no separate community edition. The client is licensed under the GNU Affero General Public License v3. Read the licensing overview for the practical details, or see CONTRIBUTING.md to help shape the project.

Acknowledgements

Flectar Mail is made possible by the work of these projects and their contributors:

• Slint, the native UI toolkit that powers the Flectar Mail interface.
• Blitz, the Rust HTML/CSS renderer from the Dioxus team that powers the email reading experience.