In order to prevent the cPanel account from receiving messages from a domain, you can use the Global Email Filters icon in cPanel.
1. Login to cPanel
2. Click on the Global Email Filters icon
3. Click the blue "Create New Filter" button
4. Create a rule with the following conditions. Please replace "exampledomain.tld" with your desired domain. You can also just put part of a domain. In this example, you could put ".tld" to block messages from all domains that have .tld in them.
From - Contains - exampledomain.tld - Discard Message
5. Click the blue "Create" button