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.

Benefit	Details
Fast from the first click	A native interface and local-first data path get you to your inbox without waiting on a browser runtime.
About 20 MB of private memory at idle	About 85 MB counting its code and libraries, and a twelfth of Thunderbird's private memory with the same mailbox. See Performance.
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 stays useful without a connection.
Works with your accounts	Gmail, Outlook and Microsoft 365, or standards-based IMAP, POP3, SMTP, JMAP, CalDAV, and CardDAV services.
Privacy-conscious defaults	Remote images are blocked until you allow them, so tracking pixels can't report when you read a message.
Security by architecture	Email is never opened in a WebView. A Rust-native pipeline renders its HTML and CSS without running email scripts, avoiding the embedded-browser attack surface.
An experimental Rust renderer	Rendering email without a browser engine is new territory. Complex messages may not render correctly yet while compatibility improves.
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, not a browser wrapped in a window, and released under the AGPLv3.

⚡ Performance

Idle, same mailbox	Private memory	Including code and libraries (PSS)	Renders email with
Flectar Mail	17.2 – 17.4 MiB	79.1 – 80.0 MiB	Blitz
Geary 46	126.1 – 126.2 MiB (+629%)	309.6 – 311.4 MiB (+290%)	WebKitGTK
Evolution 3.56	191.0 – 192.2 MiB (+1,008%)	395.0 – 395.9 MiB (+397%)	WebKitGTK
Thunderbird 159	244.1 – 248.1 MiB (+1,323%)	424.4 – 427.1 MiB (+435%)	Gecko
Betterbird 153	243.9 – 247.8 MiB (+1,321%)	411.9 – 419.7 MiB (+423%)	Gecko
Mailspring 1.26	311.4 – 314.9 MiB (+1,710%)	551.1 – 551.7 MiB (+593%)	Chromium
Aerion 0.3.6	421.9 – 437.3 MiB (+2,383%)	660.4 – 678.0 MiB (+741%)	WebKitGTK

Measured on Linux with one IMAP account (860 messages), the inbox open and an HTML newsletter displayed, 60 seconds after launch, with the default CPU renderer. Each range covers two runs, and each percentage shows how much more memory an app uses than Flectar Mail, comparing the means of those runs. Every process an app starts is counted. Private memory is what Windows Task Manager lists as Memory. On Windows, with 7 real accounts and about 69,000 unread messages, Task Manager showed 37.8 MiB with the window open and 4.2 MiB once it was closed to the tray. See how we measure and how to check it yourself.

How it compares

Email client	Interface	Renders email with	Platforms
Flectar Mail	Native Rust app	Blitz, a Rust HTML/CSS renderer; no WebView	Windows, macOS, Linux, Android, iOS (sideloaded)
Thunderbird	Gecko-based desktop app	Gecko	Windows, macOS, Linux, Android
Outlook for Windows	Windows shell with a web UI	Microsoft Edge WebView2	Windows
Spark	Electron app	Chromium	macOS, Windows, iOS, Android
Aerion	Go app with a Wails web UI	System WebView	Linux, macOS, Windows
Gmail in a browser tab	Web app	Chrome or another browser	Web

✨ Features

Feature	What it does
Conversation threads	Groups replies in chronological order, with full keyboard navigation. You can turn it off.
Tabs	Browser-style tabs that remember their place, with shortcuts on desktop and a tab switcher on phones.
Profiles and account colors	Groups accounts into profiles such as Work or Personal and color-codes every message.
Appearance	Full or minimal layout, light or dark theme, color palettes, sender avatars and app icon colors.
Frameless window	Window controls in the toolbar that keep each platform's behavior.
Calendar, contacts, and files	CalDAV and CardDAV sync, JMAP and WebDAV files, attachment search, offline files and previews.
Signatures and OpenPGP	Named signatures, and OpenPGP/MIME signing and encryption on desktop through GnuPG.
Storage and backups	Space used per type, database snapshots, account backups and POP3 server rules.
Importing accounts and mail	Thunderbird, K-9 Mail, mbox, .eml, maildir, Apple Mail and ZIP archives.
HTML rendering	Email HTML rendered in Rust with Blitz, on the CPU or the GPU.

Full and minimal workspaces

Full workspace	Minimal workspace

Tabs, conversations, and profiles

Tabs	Conversation	Profile colors

Color palettes

Teal	Green	Purple	Custom

Frameless window

macOS	Windows
Linux (GNOME)	Linux (KDE)

Calendar, contacts, and files

Calendar	Contacts	Files (WebDAV/JMAP)

Made for smaller screens

Light	Dark

🧪 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.

Flectar Mail renders email with Blitz, a Rust HTML/CSS renderer from the Dioxus team, instead of embedding a browser or WebView. If a message renders incorrectly, please report it. Read more about the renderer and the CPU and GPU options.

📥 Get Flectar Mail

Flectar Mail is in development and not yet stable. Preview builds are on GitHub Releases.

[!WARNING] Google OAuth verification requires an annual CASA security assessment. Flectar is a community open-source project, so completing this assessment depends on sponsor support. Until the required verification is funded and complete, a stable release with Gmail OAuth configured by default will not be possible. If you want to help make built-in Gmail sign-in available, please sponsor Flectar.

Platform	Download	Notes
Linux x64 and arm64	AppImage, Debian/Ubuntu .deb, Fedora 43/44 .rpm, or a Flatpak bundle	Needs a Secret Service keyring. The Flatpak is a sideloaded preview, not on Flathub yet.
Windows x64 and arm64	Setup .exe or portable ZIP	Unsigned previews
macOS 14+ (Apple silicon or Intel)	DMG or application ZIP	Ad-hoc signed, not notarized
Android 8.0+ (arm64)	Signed APK	Previews and stable releases share one app identity.
iOS 17+ (iPhone and iPad)	Unsigned .ipa	Sideload it with AltStore, SideStore, or Sideloadly and your Apple ID.
HarmonyOS and OpenHarmony	Community port by springmin	Not part of GitHub releases; build it from source.

Builds without OAuth app keys keep Gmail and Outlook sign-in disabled. Use the Sign-in settings cog on the welcome screen to add your own Google or Microsoft app registration, or connect an IMAP, POP3, or JMAP account.

The installation guide covers install commands, the Linux keyring and desktop portal, Flatpak and RPM notes, verifying downloads, Android signing, iOS sideloading, and building from source with cargo run --bin flectar-mail.

🤝 Get involved

Topic	Details
🌍 Translate	Translate the app, improve a translation, or review strings on Weblate, with no programming or GitHub experience required. Translations reach this repository as pull requests, with GitHub attribution for contributors. README translations live here; see Contributing translations.
♿ Accessibility	Keyboard navigation, light and dark themes, and flexible layouts, with work ongoing. ACCESSIBILITY.md covers current features, testing limitations, and how to report a barrier.
🔒 Security	Report vulnerabilities privately as described in SECURITY.md, and keep their details out of public issues.
🌐 Open source	One open-source application with no separate community edition, licensed under the GNU Affero General Public License v3. The licensing overview has the practical details.
🛠️ Contribute	CONTRIBUTING.md explains how 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.

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