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Repo of the Day

flectar/mail

Published: Sep 17, 2026

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Contribute to flectar/mail development by creating an account on GitHub.

Summary

Flectar Mail is an open-source email, calendar, and contacts client written in Rust that targets Windows, macOS, Linux, Android, and iOS. It uses the Slint UI toolkit and a Rust-native HTML/CSS renderer called Blitz, with the README describing it as engineered to open instantly and use as little as 20 MB of RAM. The project is in development, marked as not yet stable, and is released under AGPL-3.0.

What it is useful for

  • A single native client for email, calendars, and contacts instead of stitching together separate apps.
  • An alternative to WebView-based mail clients built with frameworks like Tauri or Wails.
  • Connecting to standards-based servers via IMAP, SMTP, JMAP, CalDAV, and CardDAV, or to Gmail, Outlook, and Microsoft 365 when OAuth is configured.
  • Local-first work, since mailboxes and calendars are stored on-device and remain usable offline.
  • Desktop OpenPGP/MIME signing and encryption through an installed GnuPG 2.x with pinentry.
  • Studying a Rust codebase that combines Slint, Blitz, and an experimental email rendering pipeline.

How engineers can use it

Pre-release builds are published on GitHub Releases for testers using their own OAuth registrations or IMAP/JMAP accounts. Documented build formats include:

  • Linux x64: AppImage, Debian/Ubuntu .deb, Fedora .rpm, or a Flatpak preview bundle
  • Windows x64: setup .exe or portable ZIP (unsigned)
  • macOS 14+: DMG or application ZIP (ad-hoc signed, not notarized)
  • Android 8.0+: experimental test APK

On Linux, install with 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 release includes SHA256SUMS and signed attestations; verify with gh attestation verify <download> --repo flectar/mail.

To build from source, install the Rust toolchain and run cargo run --bin flectar-mail. Linux desktop OAuth needs xdg-desktop-portal and a Secret Service provider like GNOME Keyring; release builds refuse to start the OAuth flow without secure credential storage.

Built-in Gmail and Outlook sign-in stay disabled until OAuth verification is funded, so testers configure their own client ID through the welcome screen's Sign-in settings or use IMAP/JMAP.

Documented limitations to keep in mind:

  • HTML rendering is the most experimental area. Complex or unusual markup may not render correctly, and the project asks users to report failures.
  • S/MIME and mobile OpenPGP are not currently supported.
  • Windows previews are unsigned, macOS previews are not notarized, and Android test APKs may require uninstalling the previous build, which deletes local app data.
  • The Flatpak preview is a standalone test bundle, not on Flathub, and its close-to-tray option is disabled until a sandbox-safe D-Bus name is available.