The Courier mail transfer agent (MTA) is an integrated mail/groupware
server based on open commodity protocols, such as ESMTP, IMAP, POP3, LDAP,
SSL, and HTTP. Courier provides ESMTP, IMAP, POP3, webmail, and mailing list
services within a single, consistent, framework.
The web-based administration and configuration tool for the Courier
mail server is capable of changing the settings of the MTA, IMAP, POP
and Webmail servers and the LDAP, MySQL and PostgreSQL authentication
modules. Only the installed parts of the Courier mail server show up
in the administration frontend.