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.
All the programs come with a basic array of features: Forwarding, Replying, Address Book, Folders, Junk mail, etc… I will not be explaining these features as these are a base for all types of e-mail programs and are irrelevant to the topic.
The most basic of these choices is SquirrelMail. It has the most basic of all interfaces.
As you can see in the photo above, it is a very basic and just lists your mail. There isn’t much to be said about this save for its simplicity.
The next is Roundcube. This has a more jazzed up interface using Ajax, this allows smoother selection of e-mail. There is no box checking, you can just click on the e-mail and use the options above the box to deal with the mail. As with SqurrielMail this is a simple interface just used for checking mail.
The is a good choice if you want a cleaner / smoother looking webmail program.
Horde is different than the other 2 webmail programs. This is a full featured e-mail program, it has similar features to Outlook.
It has a list of options (in the upper right hand corner and on the left hand side) for you to choose from: Mail, News, Calendar, Notes, Tasks. It also has the feature Layout where you can change how the home page is displayed for you when you log in to your mail.
News- Setup Subscriptions to receive mail from different sources (Sports news, Electronics, Religion, etc…)
Calendar- Allows you to setup important dates and meetings (These can be imported from other programs)
Notes- Write notes or other information down and store it for later.
Tasks- You can schedule tasks that need to be completed and keep track of their progress.
Options- Customize how the time is displayed, how the color scheme of Horde appears, along with many other settings.
In the end it really comes down to what you need: SquirrelMail for simplicity, Horde for the large amount of features, and RoundCube for the aesthetic appearance.