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Cyrus is an IMAP server, where IMAP (Internet Message Access Protocol) is a protocol for accessing mail.

The Cyrus IMAP server differs from other IMAP server implementations in that it is generally intended to be run on "sealed" servers, where normal users are not 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 content is through JMAP, IMAP, NNTP, POP3, CalDAV, CardDAV, and WebDAV protocols.

The private mailbox database design gives the server large advantages in efficiency, scalability, and administrability. Multiple concurrent read/write connections to the same mailbox are permitted. The server supports access control lists on mailboxes and storage quotas on mailbox hierarchies.

Cyrus goals

To be the best open source secure, scalable mail server, providing breadth and depth of functionality across email, contacts, calendar and related messaging services!

How to get Cyrus

Cyrus comes in three flavours:

1. Our release source tarballs from https://github.com/cyrusimap/cyrus-imapd/releases
   • Recommended for most users.
   • These are packaged by the Cyrus team.
   • The docs are pre-built for you in doc/html.
   • They're definitively tagged to a particular release version with up to date release notes.
2. Raw source from https://github.com/cyrusimap/cyrus-imapd
   • Use this if you need a version of Cyrus that contains an unreleased patch/fix/feature.
   • These bundles require a lot more dependencies to build than a packaged tarball.
3. Operating System distribution packages.
   • Cyrus IMAP packages are shipped with every major distribution, including but not limited to Fedora, Red Hat Enterprise Linux, CentOS, Scientific Linux, Debian, Ubuntu, openSUSE, Gentoo, Mageia and ClearOS.
   • Please be aware that we don't maintain these packages and as such, some distributions are out of date.
   • If you run into problems with a packed distribution, please contact the source of the distribution.

How to install Cyrus from packaged releases

Please be sure to read the documentation. The latest version is online at htt