Zimbra is the “new kid on the block” in the email world. They’ve built a beautiful AJAX based, open source application, which you can view via their Flash demo, or try through their hosted demo. I highly suggest taking a look at the Flash demo to get a better understanding of how they are creating a very user-friendly system.
In some ways, this Web 2.0 time we’re living in can feel overwhelming. There are just too many choices. You want a browser? Choose between Flock, Internet Explorer, Firefox, Opera, or Safari. You want email? Will you choose Yahoo, Hotmail, or GMail as your web-based version and Outlook, Mail, or Thunderbird as your actual client? Too many choices sometimes.
However, with all the choices out there one thing always proves out – if you build a simple and high-quality product you will win out. Google has shown us this, they entered an incredibly competitive search market at the worst possible time – and won. Zimbra could do the same thing.