The Courier mail transfer agent (MTA) is a modular multiprotocol mail server that's designed to strike a balance between reasonable performance, flexibility and features. When Courier-MTA is installed together with Courier-IMAP and SqWebMail, they form an integrated mail/groupware server suite that provides ESMTP, IMAP, POP3, webmail, and mailing list services within a single, consistent framework. A web-based administration and configuration tool is included for comprehensive configuration of the entire Courier software suite.