MailOS

Free business email on your own domain.
Mailboxes, calendar, booking page and file Drive for your whole team, running on your own Cloudflare account.
Free and open source, by 14 Technologies.

Try the live demo · Install free · Setup guide (PDF) · Support

Free means free

MailOS is free to install and use. No trial, no card, no per-user fee.

What you get free
Mailboxes on your domain	10 (info@, sales@, you@ …)
Web app and phone app	Install from the browser on Android, iPhone and desktop, with instant notifications
Calendar	Events, invitations and reminders
Booking page	A public link where clients pick a free slot
Drive	1 GB per person for files and sharing
Spam filter, rules, search	Included
Your data	Stays on your own Cloudflare account

Sending and receiving cost nothing too: Cloudflare Email Routing receives mail free, and Resend's free tier sends 3,000 emails a month.

Android app

⬇ Download MailOS for Android (latest APK)

Version 1.0.5 · direct link · SHA-256 d2fda641af822cc5ebb09c69ae467cd083ee07e3d9926118211cc56c533dc4c0

1. Open the link on your Android phone and download the APK.
2. Tap the file. If Android asks, allow installing apps from your browser or Files app (Install unknown apps).
3. Open MailOS, enter your MailOS address (e.g. https://mail.yourcompany.com) once, and sign in.

Opens straight into your inbox, full screen, with background new-mail notifications, downloads to your Downloads folder, and the phone's back button closing menus and the composer first. The APK is sideloaded (not from Google Play yet), so Android shows its usual "unknown app" prompt; the SHA-256 above lets you check the file. Prefer no install? Open your MailOS address in Chrome and choose Add to Home screen.

Install free

You need a domain (for example yourcompany.com) on a free Cloudflare account.

1. Deploy. Click Deploy to Cloudflare above. Keep the Worker name mailos (an internal name; changing it breaks mail routing).
2. Create your admin. Open the app at /setup and create your admin account.
3. Connect your domain. Add your domain, choose how to send (Resend free tier is easiest), then create your mailboxes.

CF_TOKEN is required. Create a scoped Cloudflare API token and save it as the Worker secret CF_TOKEN:

• All accounts: Email Sending:Edit, DNS Settings:Edit, Email Routing Addresses:Edit
• All zones: DNS Settings:Edit, Email Routing Rules:Edit, Zone Settings:Edit, DNS:Edit

The illustrated setup guide (PDF) walks through every screen. More options: deployment guide.

Install with an AI agent

Paste this into an AI agent with terminal access (Codex, Cursor and similar):

Install MailOS for me from https://github.com/14technologies/mailos on my Cloudflare account.

1. Read README.md, docs/deployment.md and wrangler.jsonc first.
2. Ask me for my Cloudflare account ID and two API tokens, using a secret input:
   a deploy token (for Wrangler) and a runtime token (the Worker secret CF_TOKEN).
   Never print them, commit them, or pass them as command arguments.
3. Keep the Worker name exactly "mailos". Create or reuse the D1 database
   "mailos", the R2 bucket "mailos-raw", and the queues "mailos-inbound",
   "mailos-outbound" and "mailos-agent".
4. Install dependencies, run `npm run deploy`, and set CF_TOKEN as a Worker secret.
   Do not run remote database migrations yourself. The /setup page does that.
5. Give me the app URL and anything I still need to do. I will open /setup, create
   the admin account and connect my domain.

Self-host with Docker

Runs as one container on any server, with SQLite and local files.

cp .env.docker.example .env.docker
docker compose up -d --build

See self-hosting.

Gmail, Outlook and Thunderbird

The optional MailOS bridge adds POP3 and SMTP so desktop and phone mail apps can sign in. It runs on any small Linux server.

Features

• Email: personal and shared mailboxes on your domain, conversations, instant search, snooze, follow-up reminders, read receipts, signatures and profile pictures.
• Routing rules: store, forward, reject or sort incoming mail.
• Calendar: repeating events with time zones; attendees get email invitations.
• Booking: a public link so anyone can book a free time on your calendar.
• Drive: store and share files.
• Phone app: installs from the browser, with push notifications.
• Admin: users, domains, API keys, webhooks, audit logs and backups.
• Import: bring in mail from IMAP, Gmail Takeout, .eml and .mbox files.
• Flexible hosting: Cloudflare Workers or Docker; D1, PostgreSQL, MySQL or Turso; R2, Backblaze B2 or AWS S3.
• 34 languages, including اردو, हिन्दी, বাংলা, العربية and English.

Optional upgrade

Most small teams never need one. If you grow past 10 mailboxes, MailOS Pro and MailOS Team add more mailboxes and logins, extra domains, more Drive space, the AI assistant, your own branding and priority help. A licence key unlocks them in Admin → Upgrade; nothing is reinstalled. Details at 14technologies.com/products/mailos.

Support

• Questions and bugs: GitHub Issues
• Setup help: the setup guide (PDF), or ask 14 Technologies to set it up with you at 14technologies.com

Local development

cp .dev.vars.example .dev.vars
npm install
npm run db:migrate:local
npm run dev

Add your Cloudflare credentials to .dev.vars, then open localhost:3000. Run npm run db:seed to load sample data. A schema change needs a migration for each database type; see Databases.

Documentation

• Deployment and configuration
• Databases
• Sending and receiving providers
• API and integrations
• Email assistant and MCP
• Adding a language
• Troubleshooting

Licence

MailOS is made by 14 Technologies and released as open source under the GNU AGPL v3: you may use, change and share it, and if you run a changed version for others you must share your changes under the same licence. See NOTICE.