Mozilla didn’t stop with Firefox, they also made a great email client. It is much easier to use than Outlook, especially when moving email messages from one computer to another. All of the email messages are stored as simple text files, in a standard format that almost any program can read, so you can export your emails to other programs if you want (but who would want?).
Email clients as software are a little old fashioned. Many students use web-based email programs, such as Hotmail, Yahoo Mail or Gmail from Google. Actually, among seven different ways to communication electronically, university students use email the least. More about the other ways to communicate with students in other tools.