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.

• 快递邮件传输代理（MTA）是一个综合性的电子邮件/群件服务器基于开放商品协议，如esmtp，IMAP的，支持POP3，LDAP的，SSL和HTTP的。