SendGate — Self-Hosted Email Validation Utility

SendGate is a lightweight, stateless utility for email validation and risk assessment. It identifies potential bounces, spam traps, and infrastructure patterns that could damage your domain reputation.

Built for developers, agencies, and privacy-sensitive businesses. MIT Licensed.

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Key Features

• Privacy First: SendGate does not store email lists or analysis results. All processing happens in-memory.
• Stateless Analysis: No database required. We don't store your emails.
• REST API: Real-time single email verification for your apps.
• Bulk CSV Support: Process lists with configurable size limits (MAX_BULK_EMAILS).
• Infrastructure Signals: Deep assessment of SPF, DMARC, MX records, and known provider patterns.
• Self-Hosted: Run it on your own infrastructure via Docker for total data control.

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Quick Start

1. Run with Docker

docker run -p 3000:3000 \
  -e SENDGATE_API_KEY=your_secret_key \
  -e APP_BASE_URL=http://localhost:3000 \
  ghcr.io/igorfilippov3/sendgate:latest

2. Manual Setup

git clone https://github.com/IgorFilippov3/sendgate.git
cd sendgate
npm install
npm run build
npm start

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Privacy

SendGate does not store email lists or analysis results. All processing happens in-memory unless explicitly modified by the host. This makes it ideal for handling PII and sensitive contact lists.

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Configuration

Variable	Description	Default
SENDGATE_API_KEY	Key for API authentication. If not set, API is disabled.	-
MAX_BULK_EMAILS	Max emails per CSV upload. Use with caution (memory impact).	100
APP_BASE_URL	Base URL for absolute links and metadata.	http://localhost:3000
APP_VERSION	Current application version for health reporting.	0.1.0

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API Reference

Analyze Single Email

POST /api/v1/analyze/single

Headers: Authorization: Bearer YOUR_API_KEY

Request Body:

{
  "email": "test@example.com",
  "sandbox": false
}

Response:

{
  "email": "test@example.com",
  "risk": "safe",
  "score": 95,
  "details": {
    "is_disposable": false,
    "has_mx": true,
    "has_spf": true,
    "has_dmarc": true
  },
  "findings": [
    "Verified provider configuration",
    "Standard shared infrastructure"
  ]
}

Health Check

GET /api/health

No authentication required. Returns the current status and version of the instance.

Response:

{
  "status": "healthy",
  "timestamp": "2026-02-05T12:00:00.000Z",
  "version": "0.1.0",
  "uptime": 1234.56,
  "env": "production"
}

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How It Works

SendGate assesses risk based on four primary categories:

1. Authentication: Validation of SPF and DMARC policies.
2. Infrastructure: Analysis of MX records, TLS paths, and infrastructure signals.
3. Reputation: Checks against public blocklists and historical domain signals.
4. Behavioral: Identification of catch-alls, disposable domains, and role-based addresses.

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Relationship to Senlo

SendGate is an open-source utility built by the team at Senlo.

Need a full-scale transactional email infrastructure and a beautiful drag-and-drop editor? Check out Senlo.io.

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License

MIT License. Feel free to fork, modify, and use in your own projects.