Introduction
The cPanel software comes with a feature that will allow you to define what countries will be allowed to send emails to your server:
Filter incoming emails by country
The IPs are generated based on Geolocation data, and this list is updated on every major version of cPanel, but the file is not touched until making another change. In some rare cases, the Geolocation of an IP can change.
Procedure
Access your WHM and go to Home »Email »Filter Incoming Emails by Country
Toggle any country on the list to Allow/Blocked to update the current saved IP addresses.