Using AJAX, Zimbra delivers a surprisingly rich Web-based e-mail client, but its mail server and extensive integration capabilities are equally impressive

Managing a high-volume e-mail system using traditional tools can be a demanding and costly task. That's why Zimbra wants to rewrite the book on enterprise messaging. "It's a clean-slate view of the world," says CEO Satish Dharmaraj.

The Zimbra e-mail platform is Web-based, so all administration happens centrally, at the servers. But Zimbra is not just another form of Web mail, Dharmaraj says. Its use of AJAX (Asynchronous JavaScript and XML) technology provides local caching and a sophisticated client UI, so users collaborate in a familiar way, reminiscent of Microsoft Outlook.

In fact, users can still use programs such as Outlook, Apple Mail, and Mozilla Thunderbird to access e-mail (Zimbra is working on an offline client, too). The product's Web UI gets it noticed, but there's a lot going on beneath the surface.

Mail data is managed through hierarchical storage, so individual mailboxes can be restored and managed -- no more restoring an entire mail directory to retrieve one user's files. To reduce storage costs, Zimbra lets IT keep current mail on a high-availability storage system and move older messages to cheaper storage. Zimbra manages the flow of data among the storage systems, so users see a unified message list no matter where the actual messages are stored.