How does webhook automation work?

The simplest way to think about webhooks: they're the opposite of polling. Instead of your system asking "did anything happen?" every few seconds, the other system tells yours "something just happened" the instant it does.

Here's a concrete email example. A subscriber clicks a link in your campaign. Your ESP registers the click event. Rather than waiting for you to pull a report later, the ESP immediately sends an HTTP request to a URL you've configured. Your webhook endpoint. That request contains a payload (a JSON object) with the relevant data: which subscriber, which link, at what time. Your system receives it, does whatever you've set up (log it, trigger a follow-up sequence, update a CRM record), and sends back a success response.

That's an outbound webhook from your ESP to your systems. There are also inbound webhooks running the other direction: your CRM notices a contact became a paying customer and sends a webhook to your ESP, which triggers a welcome onboarding sequence.

The critical parts of the setup:

The endpoint URL: A URL on your server (or a tool like Zapier/Make) that's configured to receive POST requests. It needs to be publicly reachable and respond quickly. Most webhook senders expect a 200 response within a few seconds or they'll consider the delivery failed and retry.

The payload: The JSON data in the request body. Different ESP events send different payloads. Your code needs to parse this to extract what you need.

Authentication: Most webhook implementations include a shared secret or signature header so your endpoint can verify the request actually came from your ESP, not a random third party.

So if you're debugging webhook delivery, check your endpoint's logs first. Most problems are either parsing errors or missed API authentication steps.