prism/proton-bridge/README.md

SUP ProtonMail Bridge

IMAP bridge that monitors a ProtonMail account via Proton Bridge and sends notifications to a SUP server.

Architecture

ProtonMail (E2EE) → Proton Bridge (IMAP) → This Bridge → SUP Server → Signal → Phone

Prerequisites

1. Proton Bridge installed and running locally

   • Download from: https://proton.me/mail/bridge
   • Set up your ProtonMail account
   • Note the generated IMAP password (not your ProtonMail password!)

2. SUP Server running

   • See main README for SUP server setup

Configuration

1. Copy .env.example to .env:

   cp .env.example .env
   

2. Configure your settings:

   PROTON_EMAIL=your-email@protonmail.com
   PROTON_PASSWORD=bridge-generated-password  # From Proton Bridge settings
   SUP_SERVER_URL=http://localhost:8080
   SUP_API_KEY=your-api-key                   # Optional
   SUP_TOPIC=protonmail
   

Running Locally

# Install dependencies
bun install

# Run in development mode (auto-reload)
bun dev

# Run in production mode
bun start

Running with Docker

# Build
docker build -t sup-proton-bridge .

# Run
docker run -d \
  --name sup-proton-bridge \
  --env-file .env \
  --network host \
  sup-proton-bridge

Running with Docker Compose

See the main docker-compose.yml in the repo root.

How It Works

1. Connects to Proton Bridge via IMAP (localhost:1143)
2. Opens INBOX and enters IDLE mode
3. When new mail arrives, fetches sender and subject
4. Sends notification to SUP server at /notify/protonmail
5. SUP delivers notification via Signal to your phone

Security Notes

• Proton Bridge runs locally and handles E2EE decryption
• This bridge only accesses the already-decrypted IMAP interface
• No credentials are sent to SUP server
• Only email metadata (sender, subject) is transmitted