A Simple Mail Transfer Protocol (SMTP) host through which a company routes all its outgoing messages. The SMTP service of Internet Information Services (IIS) on Microsoft Windows 2000 can forward all outbound messages to a specified smart host. You can also configure the Internet Mail Service on Microsoft Exchange Server to forward all outgoing SMTP mail to a specific SMTP host on the Internet. Exchange Server itself can also function as a smart host for other SMTP mail servers. By using a smart host, you can offload some of the SMTP mail processing functions of your corporate SMTP mail server.