How do I test email webhooks locally?

You can test email webhooks locally in a few practical ways, depending on whether you mean incoming email webhooks (e.g. Mailgun/Postmark/SendGrid/Mailchimp “email received” events) or outgoing event webhooks (delivery/open/click events). For most local development, the easiest approach is:

1) Run a local HTTP endpoint

Create a route in your app that accepts POST requests.

Example:

• POST /webhooks/email
• log the raw body
• return 200 OK quickly

Make sure it can handle the content type your provider sends:

• application/x-www-form-urlencoded
• application/json
• raw MIME payloads for inbound email

2) Expose localhost to the internet

Email providers need a public URL to reach your webhook. Use one of:

• ngrok
• Cloudflare Tunnel
• localtunnel
• Tailscale Funnel (if available in your setup)

Example with ngrok:

ngrok http 3000

Then set your provider’s webhook URL to:

https://<random>.ngrok.io/webhooks/email

3) Send a real test event from the provider

Most providers have a “Send test webhook” button in their dashboard.

If not, trigger a real event:

• send an email to your inbound address
• request delivery/open/click events by sending yourself a message and opening it
• configure a sandbox/test mailbox if the provider supports it

4) Verify the payload

Check:

• headers/signature
• body format
• retries
• duplicate deliveries
• response time

Log the raw request body before parsing so you can debug signature verification and payload format issues.

5) Use a webhook inspection tool

If you just want to simulate webhooks locally without a real email provider:

• RequestBin / webhook.site
• Pipedream
• Postman mock servers
• a local test script that POSTs sample payloads to your endpoint

6) Test signature validation

If the provider signs webhooks:

• copy a real test payload
• compute signature using the provider secret
• verify your code rejects invalid signatures

Example workflow

1. Start your app locally on port 3000.
2. Run ngrok http 3000.
3. Paste the ngrok URL into your provider’s webhook settings.
4. Send a test email or trigger the event.
5. Inspect logs and fix parsing/authentication issues.

Common pitfalls

• forgetting to handle URL-encoded bodies
• not reading the raw body before JSON parsing
• responding too slowly (providers may retry)
• assuming local localhost is reachable from the internet
• ignoring duplicate webhook deliveries

If you tell me which email provider you’re using (SendGrid, Mailgun, Postmark, AWS SES, etc.) and your stack (Node, Python, Rails, etc.), I can give you exact local testing steps and sample code.