Quatrelle

Why Quatrelle

• Familiar. Three panes, the ribbon's everyday buttons and the shortcuts people already use: Ctrl+N new, Ctrl+R reply, Ctrl+Shift+R reply all, Ctrl+F forward, Ctrl+Q / Ctrl+U read / unread, Insert flag, Delete, Backspace archive, Ctrl+Shift+V move, F9 send / receive, Ctrl+Enter send, Ctrl+E search, ↑ ↓ to walk the list. Drag messages onto a folder to move them.
• Local-first. Every folder is cached on disk with the IMAP sync state (UIDVALIDITY, UIDNEXT, HIGHESTMODSEQ), so a refresh costs a handful of round trips and changes made offline are replayed when you reconnect. See docs/sync.md.
• Private. No cloud relay: the app talks to your mail servers directly over TLS. Passwords (or OAuth sign-ins) live in the OS keychain (Windows Credential Manager, macOS Keychain, Secret Service). HTML mail is shown as formatted text and pictures from the web load only when you ask, so trackers stay quiet.
• Media-aware. Picture attachments preview inline, text-like files and attached emails open in a preview, and files a Craft app edits get Open in PdfCraft / WordCraft / GridCraft…; any attachment opens in its default app or saves anywhere.
• Fast. The message list only lays out the rows on screen; search uses an inverted index over headers, cached bodies and attachment names.
• Built for agents. Every action is a command with an id. The same commands drive the ribbon, shortcuts, the CLI (quatrelle-cli run mail.reply) and startup scripting (--cmd).
• Never crash. No unwrap/expect/panic outside tests, hostile-input caps in the IMAP parser, a test that runs every command with junk parameters, and Session::run catches any panic.
• Open. MIT OR Apache-2.0, clean-room: built from the RFCs and public behaviour, every asset original but the interface icons, Microsoft's MIT-licensed Fluent UI System Icons (ATTRIBUTION.md).

The name

A quatrelle is a Renault 4L — the yellow van the postman drove from one mailbox to the next, never in a hurry and never leaving a letter behind. Ours is a little rusty in places, and that is the point: Rust is the language underneath, and the rust is what keeps it from falling apart.

What works today

Area	Highlights
Accounts	Any IMAP + SMTP or POP + SMTP provider (POP mail is kept in folders on this computer, starting from an existing .pst if wanted), JMAP (RFC 8620/8621), Exchange Online through Microsoft Graph, or an organisation's own Exchange server through EWS (NTLM or Basic sign-in, found with Autodiscover, calendars and contacts included); several accounts with an All Inboxes favorite; server settings found from the address (the domain's autoconfig, the Mozilla ISPDB, MX and SRV records); sign-in through the browser (OAuth 2.0) for Microsoft 365 with your organisation's own app registration, and for Gmail and Outlook.com in builds that carry one (docs/oauth.md), an app password otherwise; SSL/TLS or STARTTLS; passwords in the system keychain; Outlook data files (.pst) open as mailboxes of their own, with their contacts and calendar, and any account exports to one
Sync	Folder list with special-use roles (RFC 6154); per-folder incremental sync (new mail, flag changes via CONDSTORE, deletions via QRESYNC); UIDVALIDITY resets; IDLE on the Inbox for instant new mail; newest messages prefetched for offline reading; changes made offline replayed; back-off reconnects; desktop notifications for new mail
Reading	Date-grouped list (Today, Yesterday, weekdays, Last week…), unread bars and bold, flags, attachment and replied markers, previews; reading pane right, bottom or off; double-click opens a message in its own window; conversations (JWZ threading); HTML shown formatted (headings, lists, links, quotes, colours, tables) with web pictures on request, remembered per sender; picture, PDF and video thumbnails; attachments dragged out to other apps; Print, Save as PDF, Save as .eml; arranged by date, sender, recipient, subject, size, flag or attachments, either way round; filters for unread, flagged, files, categorized, important and to or Cc me; a minimizable folder pane
Organising	Delete (to Deleted Items; permanent there, with confirmation), Archive, Report junk / Not junk, Move to (dialog or drag), Read / Unread, Flag, Pin, Snooze, colour categories, Mark all as read; Focused / Other; inbox rules; filters: Unread, Flagged, Has files; multi-select with Ctrl and Shift; folders created, renamed, moved and deleted; favourites; Undo (Ctrl+Z); Ignore a conversation (its later replies go to Deleted Items)
Writing	New, Reply, Reply all, Forward (with attachments); formatting (bold, italic, lists, headings, quotes, links) sent with a plain-text alternative; pictures inserted or pasted inline; To / Cc / Bcc suggested from mail you've seen; attachments up to 25 MB; signatures; drafts saved to the server; an Outbox for mail written offline; Delay Delivery; voting buttons; High / Low importance and read receipts; drafts that can't reach the server are kept and saved when it's back; S/MIME signing and encryption, with a certificate file or a smart card; OpenPGP signing and encryption with a key Quatrelle makes or imports, the window saying whether every recipient can receive the message encrypted

The full list of what's missing, ranked, is in docs/gaps.md.

Quick start

Installers come from the Releases page: .msi and a portable zip for Windows (x64, x86, ARM64), a .dmg for macOS (universal), AppImage, .deb, .rpm, Flatpak and .tar.gz for Linux (x86_64, aarch64, riscv64), and a FreeBSD tarball. The Windows and macOS installers aren't signed yet: Windows SmartScreen asks you to confirm (More info › Run anyway), and macOS to allow the app in System Settings › Privacy & Security. Versions: 1.0.x are the stable releases and their fixes; 1.1.x test builds come first as pre-releases. To run from source:

cargo run --release -p quatrelle -- --sample

--sample opens a local-only sample mailbox, so you can try everything without a server. Run without it to add your own account (the gear button, or the welcome screen).

To keep no mail on the computer, tick Online only when adding an account (or later in File › Options › Mail): its mail stays on the server and in memory while Quatrelle runs. The Windows portable zip runs from any folder, a USB stick included: its portable.txt keeps everything Quatrelle writes in QuatrelleData beside it, and passwords only until it closes (put a portable.txt beside the app on macOS and Linux for the same).

From the command line (passwords come from QUATRELLE_PASSWORD or a prompt, never stored):

cargo run -p quatrelle-cli -- add --email [email protected]
cargo run -p quatrelle-cli -- add --email [email protected] --imap mail.example.com:993 --smtp mail.example.com:465
cargo run -p quatrelle-cli -- add --email [email protected] --jmap https://api.fastmail.com/jmap/session
cargo run -p quatrelle-cli -- test
cargo run -p quatrelle-cli -- sync
cargo run -p quatrelle-cli -- list --limit 10
cargo run -p quatrelle-cli -- search "from:zoe has:attachment"
cargo run -p quatrelle-cli -- send --to [email protected] --subject "Hello" --body "Sent from Quatrelle"
cargo run -p quatrelle-cli -- commands

The browser version (JMAP accounts; see packaging/web/README.md):

cd apps/quatrelle-web && trunk serve

Then open http://127.0.0.1:8774/?sample for the sample mailbox. The latest stable release's browser version is also at https://dgaudin.github.io/quatrelle/demo/?sample, under the website whose pages are in site/ (.github/workflows/pages.yml puts both there when a release is published or site/ changes on main).

The desktop app and the CLI share the cache (%APPDATA%\Quatrelle, ~/Library/Application Support/Quatrelle or ~/.local/share/quatrelle; override with --data DIR or QUATRELLE_DATA).

Architecture

Layer	Crate	Job
L0	model	accounts, folders, message keys, flags, jobs and events, JWZ threading, search queries and index, dates, IMAP UTF-7
L1	mime	parse messages for the list and reading pane, HTML → text, attachments, build outgoing mail, reply / forward drafts
L1	store	the local-first cache: folder state, message sources, pending offline changes, the Outbox; atomic writes
L1	print	messages as PDF pages, with the interface font embedded
L2	jmap	the JMAP transport, async over any HTTP client: the desktop's and the browser's fetch
L3	net	native only: IMAP client on imap-proto, the sync algorithm, SMTP via lettre, JMAP push, Microsoft Graph, Exchange Web Services (NTLM), CalDAV/CardDAV, ManageSieve, POP3, HTTP, DNS, autoconfig, OAuth, Outlook data files, per-account worker threads
L4	engine	the sans-I/O session: views, selection, compose, search, the command registry; queues jobs, applies events
L6	ui-egui	the egui front end (thin: reads the session, runs commands)
apps	quatrelle, quatrelle-cli, quatrelle-web	the desktop app, the command line and the browser version

The engine never touches the network: it emits Jobs and applies Events, which the app connects to the net worker pool. Tests drive it with scripted events, and in-memory IMAP and JMAP servers (and Graph, CalDAV/CardDAV and ManageSieve) servers test the real clients and sync code. Details in docs/architecture.md.

Quality gate before every commit: cargo xtask ci (fmt, clippy -D warnings, tests, layering, assets, wasm).

Packaging and releases

The scripts in packaging/ build every installer (packaging/linux/package.sh, packaging/macos/package.sh, packaging/windows/package.ps1, packaging/freebsd/package.sh), and the GitHub workflows run them through the shared Craft pipelines in storytold/craft-common-actions:

Workflow	When	What
ci.yml	every push and pull request	cargo xtask ci on Windows, macOS and Linux
freebsd.yml	pushes to main, dependency changes	build and test in a FreeBSD VM
windows-arm64.yml	pushes to main, weekly	cross-build the ARM64 MSI, install and run it on Windows 11 ARM
packaging-lint.yml	packaging or workflow changes	actionlint, shellcheck, PowerShell, WiX, desktop entry, AppStream, Flatpak
release.yml	a push to the release branch, or by hand	sign, notarize and package every platform, then draft a GitHub Release
release-from-run.yml	by hand	the draft from a release run's packages, when a platform failed for a reason outside the code
pages.yml	a stable release published, or by hand	the release's browser version on GitHub Pages: the demo

The version lives only in [workspace.package] of Cargo.toml (cargo xtask version, cargo xtask version set 0.2.0). App icons are drawn by cargo xtask icons; put a square picture of your own in assets/icon.png and run it again to use that instead.

License and credits

MIT OR Apache-2.0. Quatrelle started as a fork of ZIDAN44/mailcraft (© the ArtCraft Team and the MailCraft contributors); what it changed from it, and why, is in FORK.md (in French). The rest is © Didier Gaudin.

Built on mail-parser and mail-builder (Stalwart Labs, Apache-2.0 / MIT), imap-proto (MIT / Apache-2.0), lettre (MIT), rustls and ring, html2text (MIT), ttf-parser and miniz_oxide (MIT / Apache-2.0), quick-xml (MIT), hayro (MIT / Apache-2.0), outlook-pst-rw (MIT, Microsoft's outlook-pst reader with a writer added, built from a fixed copy), drag (MIT / Apache-2.0), x11rb (MIT / Apache-2.0) and egui. Microsoft Outlook is a trademark of Microsoft; Quatrelle is not affiliated with it and uses none of its code or assets; its interface icons are Microsoft's Fluent UI System Icons, published under the MIT licence.