The IMTA multithreaded SMTP Dispatcher is a multithreaded connection dispatching agent that permits multiple multithreaded servers to share responsibility for a given service. When using the SMTP Dispatcher, it is possible to have several multithreaded SMTP servers running concurrently. In addition to having multiple servers for a single service, each server may handle simultaneously one or more active connections.
Note - The SMTP Dispatcher is available only in the Sun Internet Mail Server 3.5 - Enterprise Edition.