Open source

Your email client, on your own server.

tresso is open core. The open source edition is a complete, self-hostable email client for one person, licensed under AGPL-3.0.

View on GitHub

Licenses

  • AGPL-3.0

    The tresso client, API and sync workers. Use it, change it, host it; share your changes when you offer it as a service.

  • MIT

    The shared libraries in packages/, like domain types and the OAuth2 PKCE client. Use them in your own projects.

What is in the open source edition

  • Accounts, mail, search and the Unified Inbox
  • Smart inboxes with rules
  • The three verdicts: do, hand over, know
  • Todos, Waiting on and the daily brief
  • Calendar with CalDAV, invitations and reminders
  • Signatures and drafts, synced
  • Attachment virus scanning
  • Web, desktop and mobile apps

What tresso Cloud will add

  • AI classification and summaries
  • AI todo extraction
  • Teams, shared inboxes and delegation
  • REST API, webhooks and MCP endpoint
  • Developer tools
  • Statistics and Year in mail

Add-ons, not lock-in

Cloud features attach as add-ons through two generic hooks. The open code defines each interface with a simple implementation, such as rule-based classification, and never depends on the Cloud. Anyone can build their own add-on the same way.

Run it yourself

You need Docker and Node 24 or newer. Go and PHP run inside containers.

  1. Start the stack

    docker compose up -d

  2. Create your user

    docker compose exec api php bin/console app:user:create [email protected] "Your Name"

  3. Install and start the web app

    npm install
npm run dev:web

Then open http://localhost:5173 and sign in. For Gmail and Microsoft 365, register an OAuth app at Google and Microsoft first; without them, IMAP accounts work. Full instructions live in the repository.

Built with

API
PHP and Symfony on FrankenPHP
Sync workers
Go
Web
Vue and TypeScript
Desktop
Tauri
Mobile
Expo
Data
PostgreSQL, Redis, S3 storage, Meilisearch
Scanning
ClamAV