Zimbra Server is an open-source email and collaboration platform that includes email, calendar, file sharing, and other tools for communication and collaboration. It is available as both a standalone server and as a cloud-based service. Some of the features of Zimbra include support for multiple languages, integration with various email clients and mobile devices, and support for various protocols such as POP, IMAP, and SMTP. Zimbra is often used by businesses and organizations as a way to manage their email and collaboration needs.