Mailchip give you the option to add a Webhook url for each Audience segment (list), here are the simple steps to get you up and running.
Step 1: Copy the Webhook URL from Meribook campaign page.
Step 2: Login to your Mailchimp account
Select your list from "Current audience" and in "Manage Audience" click on "Settings"
Select "Webhooks" from the settings page.
Click "Create New Webhook" button.
Step 5: Paste the URL from Meribook and Save.