Zimbra is the leader in next-generation, open source email, calendar, and collaboration software. Zimbra customers include: H&R Block, Bechtel, Skype, Mozilla, O’Reilly Media, Stanford University and Comcast totaling over 60 million paid mailboxes worldwide.

In February 2010, the Zimbra business unit was acquired by VMware from Yahoo! to extend their virtualization infrastructure into a more complete cloud platform. Previous to the VMware deal, Zimbra was one of the larger Web 2.0 acquisitions of 2007, when Yahoo! purchased it for $350 million.

Zimbra is a rich, web-based application, built with AJAX, and a full collaboration server. It can be deployed on-premises or hosted by a third party and run as a hosted email service. It is primarily used in the enterprise market and its competitors are Microsoft Exchange and Google Apps.

Zimbra’s popularity stems from being an open source technology platform. It is built with well-known web technologies and scales economically. The core web client and server are also open source and available to be used for free. One of the other aspects of Zimbra is all APIs are open and a framework exists to incorporate other applications and web services directly into the web experience, such as Facebook, Twitter, Saleforce.com, WebEx or an organization’s own back-office systems.