Resend Email Webhook + Inspector for DigitalOcean

A Flask webhook application for receiving and inspecting inbound emails from Resend. Includes a built-in web interface to view and debug incoming emails in real-time. Ready to deploy to DigitalOcean App Platform with one click.

Features

• 🔍 Email Inspector - Web interface to view and debug incoming emails in real-time
• 📧 Webhook Receiver - Processes email.received events from Resend
• 📊 Email Dashboard - View sender, recipients, subject, attachments at a glance
• 🔌 JSON API - Programmatic access to recent emails via /emails/json
• 💾 In-Memory Storage - Keeps last 20 emails for quick debugging (resets on restart)
• 🚀 One-Click Deploy - Deploy to DigitalOcean App Platform instantly
• 📝 Detailed Logging - All webhook events logged for debugging
• ❤️ Health Monitoring - Built-in health check endpoint

Prerequisites

Before deploying, you'll need:

1. Resend Account - Sign up at resend.com
2. Inbound Email Address - Set up in Resend:
   • Go to Resend Dashboard
   • Navigate to Emails → Receiving
   • Follow the instructions to get your inbound email address (e.g., anything@yourdomain.resend.app)
   • Any email sent to this address will trigger your webhook
3. DigitalOcean Account - Sign up at digitalocean.com (optional for local testing)

Quick Deploy to DigitalOcean

Deploy this app to DigitalOcean App Platform with one click:

After deployment:

1. Get your app URL from DigitalOcean (e.g., https://resend-webhook-xxxxx.ondigitalocean.app)
2. Configure webhook in Resend:
   • Go to Resend Dashboard → Webhooks
   • Click Add Webhook
   • Webhook URL: https://your-app-url.ondigitalocean.app/webhook
   • Select event: email.received
   • Click Add
3. Test it:
   • Send an email to your Resend inbound address
   • Visit https://your-app-url.ondigitalocean.app/emails to see it in the inspector!

Or fork and deploy manually - See detailed deployment instructions below.

---

Setup

1. Install Dependencies

# Create a virtual environment (recommended)
python3 -m venv venv
source venv/bin/activate  # On Windows: venv\Scripts\activate

# Install dependencies
pip install -r requirements.txt

2. Configure Resend Webhook

1. Go to your Resend Dashboard
2. Navigate to Webhooks section
3. Click Add Webhook
4. Enter your webhook URL (e.g., https://yourdomain.com/webhook)
5. Select the event type: email.received
6. Click Add

3. Set Up Inbound Email Address

1. In Resend dashboard, go to Emails → Receiving
2. View your inbound address (e.g., anything@your-domain.resend.app)
3. Any email sent to this address will trigger the webhook

Running the Application

Local Development

# Run the Flask app
python app.py

The app will run on http://localhost:8080 by default.

View received emails:

• Open http://localhost:8080/emails in your browser to see the email viewer
• Send a test email to your Resend inbound address
• Refresh the page to see new emails appear

Testing Locally with ngrok

To test webhooks locally, use ngrok:

# Install ngrok (if not already installed)
# Then expose your local server
ngrok http 8080

# Use the ngrok URL (e.g., https://abc123.ngrok.io/webhook) 
# as your webhook endpoint in Resend

Production Deployment

For production, use gunicorn:

gunicorn -w 4 -b 0.0.0.0:8080 app:app

Manual Deployment to DigitalOcean

If you want to customize the app before deploying, follow these steps:

Method 1: Fork and Deploy

1. Fork this repository on GitHub
2. Click the deploy button above (it will use your forked repo)
3. Or manually deploy:
   • Go to DigitalOcean App Platform
   • Click Create App
   • Choose GitHub and select your forked repository
   • DigitalOcean will auto-detect settings from the Procfile
   • Click Deploy

Method 2: Deploy Your Own Repo

1. Clone and customize:

   git clone https://github.com/ajot/resend-webhook.git
   cd resend-webhook
   # Make your changes

2. Create your own GitHub repo:

   gh repo create your-resend-webhook --public --source=. --remote=origin
   git push -u origin main

3. Deploy to DigitalOcean:

   • Go to DigitalOcean App Platform
   • Click Create App
   • Choose GitHub as your source
   • Select your repository
   • DigitalOcean will auto-detect Python and use the Procfile
   • Important: Leave "Run Command" empty (let the Procfile handle it)
   • Choose your plan (Basic $5/month is sufficient)
   • Click Create Resources

4. Configure Resend Webhook:

   • Once deployed, get your app URL (e.g., https://your-app-xxxxx.ondigitalocean.app)
   • Go to Resend Dashboard → Webhooks
   • Add webhook: https://your-app-xxxxx.ondigitalocean.app/webhook
   • Select event: email.received

Files for DigitalOcean Deployment

• ✅ Procfile - Specifies how to run the app (gunicorn command)
• ✅ requirements.txt - Python dependencies (includes gunicorn)
• ✅ app.py - Main Flask application (configured for port 8080)
• ✅ .do/deploy.template.yaml - One-click deployment configuration

Troubleshooting Deployment

Error: "No application module specified"

• This happens when the Run Command is incomplete or incorrect
• Solution: Go to Settings → Components → web → Run Command
• Either leave it empty (recommended - uses Procfile) or set it to gunicorn app:app
• Never use a partial command like gunicorn --worker-tmp-dir /dev/shm without app:app

Build fails with "invalid Procfile entry"

• Check for extra blank lines in your Procfile
• Procfile should contain only: web: gunicorn app:app

App deployed but webhook not working

• Check your Resend webhook URL includes /webhook at the end
• Verify event type is set to email.received (not email.delivered)
• Check the app logs in DigitalOcean for error messages

Custom Domain (Optional)

1. In App Platform, go to Settings → Domains
2. Add your custom domain
3. Follow DNS configuration instructions
4. Update your Resend webhook URL to use the custom domain

API Endpoints

POST /webhook

Receives inbound email webhook events from Resend.

Expected Payload:

{
  "type": "email.received",
  "created_at": "2024-02-22T23:41:12.126Z",
  "data": {
    "email_id": "56761188-7520-42d8-8898-ff6fc54ce618",
    "created_at": "2024-02-22T23:41:11.894719+00:00",
    "from": "Acme <onboarding@resend.dev>",
    "to": ["delivered@resend.dev"],
    "bcc": [],
    "cc": [],
    "message_id": "<example+123>",
    "subject": "Sending this example",
    "attachments": [
      {
        "id": "2a0c9ce0-3112-4728-976e-47ddcd16a318",
        "filename": "avatar.png",
        "content_type": "image/png",
        "content_disposition": "inline",
        "content_id": "img001"
      }
    ]
  }
}

Response:

{
  "status": "success",
  "message": "Email processed successfully",
  "result": {
    "email_id": "56761188-7520-42d8-8898-ff6fc54ce618",
    "processed_at": "2024-02-22T23:41:12.126Z",
    "status": "processed"
  }
}

GET /emails

Web interface to view recent received emails.

Features:

• Displays last 20 emails in a responsive table
• Shows: timestamp, from, to, subject, attachment count
• Click "View Details" to see full email payload
• Empty state when no emails received yet
• Styled with Tailwind CSS

Access: Visit https://your-app-url.ondigitalocean.app/emails in your browser

GET /emails/json

Returns recent emails as JSON for programmatic access.

Response:

{
  "emails": [
    {
      "email_id": "56761188-7520-42d8-8898-ff6fc54ce618",
      "from": "sender@example.com",
      "to": ["recipient@example.com"],
      "cc": [],
      "bcc": [],
      "subject": "Test email",
      "message_id": "<message@example.com>",
      "attachments": [],
      "created_at": "2024-02-22T23:41:11.894719+00:00",
      "processed_at": "2024-02-22T23:41:12.126Z"
    }
  ],
  "count": 1
}

GET /health

Health check endpoint.

Response:

{
  "status": "healthy"
}

Customization

Edit the process_inbound_email() function in app.py to add your custom logic:

• Store emails in a database
• Forward emails to another service
• Parse email content
• Download and process attachments
• Send notifications
• etc.

Environment Variables

• PORT - Port to run the application on (default: 8080)

Notes

• Email storage: Emails are stored in-memory (last 20 emails). Data resets when the app restarts. For production, consider using a database.
• The webhook currently logs all email data. Adjust logging levels in production.
• Attachment metadata is included, but actual attachment content would need to be fetched separately if needed.
• Consider adding webhook signature verification for production use.
• The /emails viewer is great for demos and testing. For production dashboards, build a proper frontend with persistent storage.