
Courier-MTA
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. Individual components can be customized, enabled or disabled at will. Certain portions of the Courier mail server - the mail filtering engine, the webmail server and the IMAP server - are also available as separate, smaller, packages that can be used with other mail servers.