🛰️ Scalar Relay

Scalar Relay is an architectural bridge designed to decouple sensitive SMTP credentials from your application logic. By utilizing a stateless HTTP-to-SMTP execution model, Scalar eliminates the need for persistent credential storage in distributed n8n, Docker, and CI/CD environments.

🚀 Key Features

• Stateless by Design: Sensitive credentials stay in one place. Your apps just need an API Key.
• Dashboard Security: Protected by a login page and password.
• Setup Wizard: Sleek onboarding to configure your SMTP settings in seconds.
• Live Feed Dashboard: Monitor the last 50 sent emails in real-time (In-memory, RAM-only).
• Test Console: Verify your SMTP connection directly from the UI.
• Gateway Mode: Allow API requests to override global credentials for complex workflows.
• Open Source & Extensible: Built with Node.js, EJS, and Tailwind CSS.

🛠️ Quick Start

Using Docker (Recommended)

docker run -d \
  -p 3000:3000 \
  -v $(pwd)/config:/app/config \
  --name scalar-relay \
  ucchash111/scalar-relay:latest

Deploying to Coolify

1. Create a new Service in Coolify.
2. Select Docker Compose.
3. Paste the contents of docker-compose.yml.
4. Add SESSION_SECRET to the environment variables.
5. Deploy. Coolify will automatically detect the health check!

Deployment & Configuration

1. Environment Variables: Clone .env.example to .env and set your SESSION_SECRET and PORT.
2. Docker: Scalar is optimized for any Docker-based registry. Point your orchestrator to the /health endpoint for automated monitoring.

🌐 Distribution & Registries

1. Coolify Service Selection

To make Scalar Relay a "Pre-selected" service in Coolify:

• Add coolify.json to the root of your repository (already included).
• Submit a PR to the Coolify Services Repository with your docker-compose.yml.
• Your service will then appear in the "Services" catalog for all Coolify users.

2. Docker Hub (Automated)

This project is configured with GitHub Actions to automatically build and push the latest image to Docker Hub on every push to main.

• Image: ucchash111/scalar-relay:latest
• To use your own registry, update .github/workflows/docker-publish.yml.

3. NPM (CLI tool)

You can also distribute Scalar as a global CLI:

• Update package.json to include "bin": { "scalar-relay": "src/index.js" }.
• Run npm publish to make it available via npm install -g.
• Users can then run scalar-relay directly.

4. GitHub Template

Turn this repository into a Template (Settings -> General -> Template Repository) so users can click "Use this template" to start their own instance.

5. Extended API

Scalar Relay includes a professional API suite for deep integration:

• GET /api/info: Instance metadata and status.
• GET /api/config: Current configuration (safe fields, requires Master Key).
• GET /api/logs: View recent relay logs (requires Master Key).
• POST /api/keys: Programmatically generate new API keys (requires Master Key).

🔌 API Usage

Send an Email

POST /api/send

Headers:

x-api-key: your_master_api_key
Content-Type: application/json

Body:

{
  "to": "[email protected]",
  "subject": "Hello from Scalar",
  "text": "Sent via Scalar Relay bridge.",
  "html": "<b>Sent via Scalar Relay bridge.</b>"
}

🛡️ Security

Scalar Relay is designed to be self-hosted. Ensure your instance is not exposed to the public internet without proper firewall rules or an auth proxy. The Master API Key is generated locally during the first-run setup.

Gateway Mode (Advanced)

Send via a different SMTP server using request-level overrides:

{
  "to": "[email protected]",
  "subject": "Overridden SMTP",
  "smtpOverride": {
    "host": "smtp.sendgrid.net",
    "port": 465,
    "user": "apikey",
    "pass": "SG.secret"
  }
}

🛠️ Infrastructure

Docker Compose

docker-compose up -d

Health Checks

Monitor the instance at GET /health.

Contributions are welcome! Please see CONTRIBUTING.md and LICENSE for details.

Built with ❤️ for the Open Source Community.