Mozilla Thunder bird is a lightning fast and real no nonsense E-mail client which lives up to the reputation of its sibling, Mozilla Firefox. It is open sourced and is fully customizable with large number of add-ons available. The main advantage of Thunderbird is its powerful spam filter. You can train the Thunder bird to catch almost all spams without loosing real mails. It is very easy to configure your mail accounts and it supports multiple accounts also. It also includes a terrific search function and built-in RSS. View screen shot.