Cyrus is an email server that was developed at the Carnegie Mellon University in Pittsburg, Pennsylvania. It provides an IMAP server, POP server, and an LMTP server and, since version 2.2.0, also supports NNTP. Cyrus makes numerous methods of authentication available to users, some of which use strong encryption. The server offers server-side email filtering with the support of a specifically developed programming language, Sieve. The mailbox database design permits several write/read operations at the same time, thereby reducing the demand on resources, which ultimately leads to improved performance. The option of using access control lists and quotas is also available.
Cyrus is Open Source software, and its source code is freely available on the project page .