With a cpanel account there are 3 different mail choices offered: Horde, SquirrelMail, and RoundCube. I am going to explain the major differences between the 3 of them and hopefully that will allow you to pick the best for your own use.
This tutorial walks you through creating a simple extension. You’ll add an icon to Google Chrome that, when clicked, displays an automatically generated page. The icon and page will look something like this: