This help page is for version 5.6. The latest available help is for version 8.2.
The Network Message Action is equivalent to doing a "net send" from the command line. It allows you to direct a message box pop-up to any particular user or computer on the network.
The client machine must be running Microsoft's Messenger service to receive and display these messages. Because of spam and security concerns, the Messenger service is not started by default on most systems.
Pressing the Message button displays the configuration dialog below. This lets you customize the message text that is sent with optional replacement variables. You can also rename the action as it shows up in the various action lists. You can reset the action to its original/default name by simply clearing the name field.