Cyrus is a highly scalable enterprise mail system designed for use in enterprise environments of various sizes using standards based technologies. Cyrus technologies scale from independent use in email departments to a system centrally managed in a large enterprise.

A full Cyrus IMAP implementation allows a seamless mail and bulletin board environment to be set up across multiple servers. It differs from other IMAP server implementations in that it is run on "sealed" servers, where users are not normally permitted to log in. The mailbox database is stored in parts of the filesystem that are private to the Cyrus IMAP system. All user access to mail is through software using the IMAP, POP3, or KPOP protocols.

This code is based on the stable Cyrus release with support for CalDAV, CardDAV and RSS added. All of the standard Cyrus IMAP daemons and utilities should be considered production quality in this release, but the HTTP support (CalDAV, CardDAV and RSS) is in beta status.