Sumolabs

Zimbra: Open source makes 6 million moves on Microsoft

Zimbra, an open source server and client technology for next-generation enterprise messaging and collaboration, recently reached 6 million paid mailboxes. As a robust and affordable alternative to Microsoft's Exchange Server, Zimbra has continued to move upmarket and achieved tremendous growth over the past six months.

Two versions of Zimbra are available: a community-supported open-source version, and a commercially supported version ("Zimbra Network") with closed-source components. This foundation in open source, and the contribution back to the open source community has made Zimbra extremely popular.