Q:

Marketing Cloud Data Extension Web Hook

Does SFMC support webhooks for unsubscribes? I have an external database that I would like to keep in sync with subscribes and unsubscribes based on email.
For those that are confused by what a WebHook is, here's a simple definition.

A WebHook is an HTTP callback: an HTTP POST that occurs when something happens; a simple event-notification via HTTP POST.
A web application implementing WebHooks will POST a message to a URL when certain things happen.

Is there anyway to configure a URL for salesforce to call when a subscriber unsubscribes or updates their preferences/profile?

A:

Salesforce Marketing Cloud just started supporting Webhooks with the January 2019 Release using Event Notification Service (ENS)

Use the Event Notification Service (ENS) API to receive notifications when certain events occur in Marketing Cloud. You can be notified when customers request password resets, get order confirmations, log in using two-factor authentication, and other events.
Example: Northern Trail Outfitters, or NTO, requests that Marketing Cloud send an online order confirmation email to a customer. The customer’s email address isn’t valid, so the ENS notifies NTO almost immediately that the order confirmation bounced. Using that feedback, NTO’s system sends the customer the order confirmation via SMS instead.

Currently, Salesforce Marketing Cloud only has 3 supported events: Supported Notification Events
This new feature was primarily created to support the New Transactional API: Send Transactional Messages with a New API
Salesforce Marketing Cloud hasn't released any plans on if they will support other Notification Events, but I am hoping they do at some point near in the future.

