This command subsumes and makes obsolete any other start-msg command that was used previously to start up a component of the MTA that the Dispatcher has been configured to manage. Specifically, you should no longer use imsimta start smtp. An attempt to execute any of the obsoleted commands causes the MTA to issue a warning.
What happens with the server processes when the Dispatcher is shut down depends upon the underlying TCP/IP package. If you modify your MTA configuration or options that apply to the Dispatcher, you must restart the Dispatcher so that the new configuration or options take effect.
imsimta restart dispatcher
Restarting the Dispatcher has the effect of shutting down the currently running Dispatcher, then immediately starting a new one.