Managing IMAP

Chapter 6. Introduction to the Cyrus IMAP Server

This chapter provides a technical overview of the features and design concepts that make up the Cyrus IMAP server. The Cyrus server wasn’t the first IMAP server, nor was it written by the author of the IMAP standard. True believers in the Cyrus server and its derivatives are likely to tell you, though, that once you’ve deployed the Cyrus server, you’re unlikely to switch to another server. Cyrus boasts a very attractive feature set. It offers robust administration, scalability, and leading-edge IMAP extensions, such as mailbox quotas, plug-in authentication mechanisms, and support for server-side filtering. Detractors are likely to say that UW can be deployed more easily and that Cyrus may not make much sense for a small or medium-size user base.

The Cyrus IMAP server is based on IETF standard protocols, including IMAP4, IMSP, SMTP, RFC 822, MIME, and SASL. IMAP2bis is also supported for backward compatibility with earlier IMAP clients. POP3 is included to support POP users while they’re going through the process of selecting an IMAP client.

The Cyrus server is feature-rich, and implements several IMAP protocol extensions, including the IMAP QUOTA and the IMAP ACL extensions. Cyrus is normally run as a “black box” server—users are not meant to access the system by any means other than the IMAP protocol. Mailboxes are stored in a central location and in parts of the filesystem that are private to the Cyrus server. Cyrus was designed ...