Two things will struck me when I checked out the demo of Zimbra, an open source webmail and calendar suite: One, "Wow, this looks and works a lot like Gmail," and two, "This is open-source software??" Zimbra is seriously slick to a degree seen infrequently in new open source projects. There's a lot of Gmail in there: The popular conversation view--a feature I hope every e-mail client includes a year from now--is there, though it works a bit differently when reading messages and can optionally be turned off. Labels are there, too, though Zimbra calls them tags and uses a nice color-coded icon approach. And like Gmail, each conversation's subject is accompanied by a snipped of the body, you can add a flag to any message akin to Gmail's stars, and there's a big search bar right at the top of the app.

On top of all the Gmail-inspired features, however, Zimbra heaps tons more. Hovering over a message yields a short preview of the message, and hovering over a contact's name or e-mail address wherever it appears will show you all of their stored information, e.g. company, title, phone number, etc., and you can drag-and-drop messages onto folders or labels. And then there's the calendar, which is integrated into the e-mail compontent in a very handy way: when you see a date in a message you can hover over it to see if you have any appointments scheduled that day or right-click to add a new appointment to your calendar.

I won't even go into the developer APIs, but for the curious, Zimbra is build in Java and supports POP and IMAP and lots of other acronyms, includes spam and virus protection and, of course, is free to download.