Set up an outbound webhook

An outbound webhook does the opposite of an inbound one: Mailbo notifies your system when something happens (a new subscriber, an unsubscribe, etc.), so you can keep other tools in sync.

Step 1 — Add the webhook

1. Go to Settings → Outbound webhooks.

2. Click Add webhook.
3. Enter the URL on your server that should receive the events, and choose which events to subscribe to.

Each delivery is sent as JSON to your URL.

Step 2 — Verify the signature (important)

So you can trust that a request genuinely came from Mailbo, every delivery is signed:

• Mailbo sends two headers: x-mailbo-event (the event type) and x-mailbo-signature.
• The signature is sha256=<hex> — an HMAC-SHA256 over the raw JSON body, using your webhook's secret.

On your server, compute the same HMAC over the raw body with your secret and compare it to the x-mailbo-signature header. If they don't match, reject the request. This prevents anyone from spoofing events to your endpoint.

Step 3 — Respond quickly

Your endpoint should return a success status fast (do heavy work in the background). Webhook senders generally retry on failure, so make your handler idempotent — safe to receive the same event more than once.

Use cases

• Mirror new subscribers into your CRM or data warehouse.
• Trigger internal alerts (e.g. post to Slack when a VIP unsubscribes).
• Keep a backup of events in your own database.

Next: Create an API key