The dispatcher is another process that is always present on a Messaging Server system. It is a multithreaded traffic dispatcher, which dispatches incoming SMTP or LMTP connections to the pool of SMTP or LMTP server threads for protocol-specific processing. The SMTP and LMTP server programs provide a pool of worker threads at the disposal of the dispatcher. After it processes a message by either rejecting the message or enqueuing it into its destination channel, the worker thread is ready to accept more work from the dispatcher.
The dispatcher can block incoming traffic based on IP address and throttles it to prevent denial of service attacks. It also creates and shuts down SMTP or LMTP server processes based on load and configuration. Therefore the SMTP or LMTP slave channel programs are under the control of the dispatcher, not the job controller.