An email, calendar, contacts and tasks client with a fast Rust core, a modern UI you can reshape, and your data on your machine.
Windows desktop app · web UI · MCP access for AI agents · plug-ins

Tour · Features · Getting started · Architecture · Manual · License

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Why “Nail”?

Because it is the last nail in Outlook’s coffin. Nail does what a desktop mail client should do (many accounts in one inbox, real conversations, a calendar that speaks every protocol, solid encryption) without the weight, the lock-in or the ads. And everything you see is defined by two plain text files, so nothing about it is set in stone.

A tour

Safe by default

HTML mail renders in a sandbox that never runs scripts, remote images stay blocked until you allow a sender, links that hide their real target and senders that disguise themselves are flagged, and the complete source of every message is one click away.

Conversations that read like a conversation

Rows group a whole thread, your own replies from Sent included. The reader shows it as a feed of cards: the unread message and the newest open, older ones folded away until you want them.

Triage in one click, undo in one click

Archive, delete, label, snooze or move a whole conversation at once. Every action can be undone, also when an AI agent or a plug-in did it.

Five themes, live

Frost, Nocturne, Sage, Graphite and High contrast ship built in, each in a comfortable and a compact density, or following Windows' light and dark mode. Every colour, size and pane is a token in theme.kdl and layout.kdl, editable in the app or in any text editor.

Arrange it your way

Customize the layout right in the window: pick a preset, drag panes to another side, hide or remove them, and add widgets such as a mini calendar or today's agenda. Every change is undoable and lands in layout.kdl; toolbars can be customized the same way.

Every action a few keys away

Ctrl+K opens the command palette with every action of the app; key sequences like g c (go to the calendar) work too.

Your folders, on the server

Create, rename, move and delete folders right from the folder pane. Changes are queued, work offline and reach the server in order.

Writing

Plain text, HTML or Markdown, signing and encryption (OpenPGP with Autocrypt, or S/MIME) per message, send later, and drafts that are saved as you type.

The calendar, too

Day, week, month, year, agenda and free-time views across CalDAV, Exchange, Google and subscribed ICS calendars, with invitations answered right from the mail.

What Nail does

• Accounts: IMAP (with IDLE), POP3, SMTP, Gmail API, Exchange Online (Graph) and Exchange Server (EWS), CalDAV / CardDAV, ICS subscriptions; setup finds the settings from the address
• Mail: Unified inbox, conversations, fast full-text and server search, rules (also as Sieve on the server), snooze, junk filtering, Focused Inbox, labels and categories, vacation replies, send later
• Calendar, contacts, tasks: Every view of a calendar, invitations and free/busy (iTIP / iMIP), address books, to-dos, reminders
• Security: OpenPGP and S/MIME with Autocrypt, smart cards, sender authentication (DKIM, SPF, DMARC) per message, sandboxed HTML, remote content through a privacy proxy, look-alike sender and link warnings, encrypted local store
• Customization: Themes and layouts as plain KDL files with in-app editors, movable and resizable windows, a toolbar customizer, responsive from phone to wide screen
• Automation: An MCP server, so AI agents can read and act on mail and calendars with per-action approval; JavaScript plug-ins with a typed API and npm create nail-plugin
• Desktop: Windows installer and updates, tray and start minimized, default mail app with Simple MAPI ("Send to mail recipient"), print to PDF
• Everywhere else: nail serve runs the same UI in a browser; the remote UI is protected by passkeys or password + TOTP
• Your data: Import from and export to standard formats, backups, a recovery key; nothing leaves your machine unless you send it

Getting started

Nail is at version 0.8.0, a preview for Windows; macOS, Linux and mobile come later. Until the first release is published, build it from source:

npm ci                                              # npm workspaces: ui, e2e, packages
npm run build                                       # the UI (ui/dist)
cargo run -p nail-cli -- serve --seed demo --open   # the web UI with demo mail
npm run tauri dev                                   # the desktop app with hot reload

Prerequisites (Rust stable with MSVC, Node 26), every command, the test suites and the installer build are in docs/dev-setup.md. The user manual is in userDocs/en/.

How it is built

flowchart LR
  subgraph clients [Clients]
    desktop["Desktop app<br/>(Tauri 2, WebView2)"]
    web["Browser<br/>(nail serve, remote UI)"]
    agents["AI agents<br/>(MCP)"]
    plugins["Plug-ins<br/>(JavaScript, sandboxed)"]
  end
  ui["React UI<br/>layout.kdl + theme.kdl"]
  core["Rust core<br/>accounts, sync, operation queue,<br/>search, rules, crypto"]
  store[("Encrypted SQLite<br/>store")]
  servers["Mail and PIM servers<br/>IMAP · SMTP · Gmail · Exchange · DAV"]
  desktop --> ui
  web --> ui
  ui -- NailClient --> core
  agents --> core
  plugins --> core
  core <--> store
  core <--> servers

Loading

The core owns all data and logic; every write goes through one operation queue, so offline work, undo and agents behave the same everywhere. The UI is a renderer for layout.kdl and theme.kdl; every text comes from Fluent catalogs. Where the code lives: docs/architecture.md; the design: docs/design.md; decisions: docs/adr/.

The animations on this page are recorded from the demo data with npm run readme:media.

License

Nail is licensed under the GNU Affero General Public License v3.0 or later: you may use, change and share it, also commercially; if you distribute a changed Nail or offer it to others over a network, you make its source available under the same license. Other license terms (for example for a closed product built on Nail) are available from the maintainer.

The plug-in kit (packages/plugin-api, packages/create-nail-plugin) and the example plug-ins are MIT-licensed, so plug-ins can use any license.

Contributions are welcome under the contributor license agreement in CONTRIBUTING.md.

Nail is an independent project and is not affiliated with Microsoft. Outlook is a trademark of Microsoft Corporation.