Courier Mail Server

The Courier Mail Server is a mail server and free software. It is primarily designed as a mail transfer agent and server for IMAP.

Courier saved from the beginning in the Maildir format of qmail and led the one for IMAP, while other servers initially stayed with mbox formats. With the development of Courier was the extension of the folders and maildir quotas, called Maildir .

Courier is one of the three popular open down servers for large installations of IMAP, and is designed safer than the others. It is used, for example, from the University of Florida. The University was very early in the development.

The configuration is done with individual files or folders by the same name, from which the server reads all the files. Many of the configuration files of the Courier can be disassembled as needed and summarized again. This allows clear configuration at every scope.

The structure of Courier is modular. Mail drop, his mail delivery agent, as well as the modules for webmail and IMAP are also available separately for combination with other servers.



Authenticating Courier may be coupled to the operating system take place using a separate database, and on the basis of external directories. It is operated by a separate system service, which in turn can load modules for DBM, Pluggable Authentication Modules, MySQL, PostgreSQL, and the Lightweight Directory Access Protocol.


The module SqWebMail has the peculiarity that it is based directly on Maildir.


The history of Courier started in 1997 with the approach of mail servers should recognize spam immediately and refuse. The first version of Courier was then developed in 1999 as a mail transfer agent for the Extended Simple Mail Transfer Protocol, parallel to the module for IMAP.


Critics of the server accuse its author that he did not fully adheres to the IMAP component (Courier - IMAP ) to the rules specified in the RFCs. The author of the server denies this, however, and called the criticism as a smear campaign against his server because it was one of the first who implemented the efficient Maildir format.