Nirvana is an open source email client written in Java,
C, and C++. It is coded using SWT and SwingWT. The first in it's class. Nirvana
combines SWT's native look and feel with outstanding graphics and an intuitive
user interface to create arguably the easiest to use email client ever. Packed
with next generation features along side of old stand-bys, you'll find enough to
keep you interested and enough to feel like it's an old friend.
Not every email client is perfect, that's why Nirvana includes mechanisms to contact us, and to automatically report bugs and failures in the program so that we can make Nirvana better for you.
So, the bottom line: What does Nirvana have that could possibly induce you to switch? The answer is: That's up to you! At the moment, Nirvana is in development. As such, it's like a lump of clay, waiting for the potter to shape it. In this case, we're the potter, you are the designer. If you say that you want Nirvana to animate Ring-Around-the-Rosy every time you receive an email, we'll make every effort to implement that. We are depending on you to determine exactly what should go into this email client. And that is what I consider the most important feature of Nirvana.
Click on this link to get more detail: http://nirvana.sourceforge.net/
Recommend the tutorial