When defining the action flow of your action, you can asynchronously start an SMS flow. This behavior is implemented through the Start iSMS element which you can drag onto your canvas from the Action Flow Toolbox.
Start iSMS is available in the following situations:
Message Queues Component is installed in your server. If this component is not installed, a warning message is presented and you should contact your Service Center administrator.
iSMS Flow Initiated by Another Flow | Start iSMS Tool Properties | Action Flow Toolbox