Zimbra is open source server software for email and collaboration - email, group calendar, contacts, instant messaging, file storage and web document management. The Zimbra email and calendar server is available for Linux, Mac OS X and virtualization platforms. Zimbra syncs to smartphones (iPhone, BlackBerry) and desktop clients like Outlook and Thunderbird. Zimbra also features archiving and discovery for compliance. Zimbra can be deployed on-premises or as a hosted email solution.
http://www.zimbra.com
