How do I determine who site participants can send a message to?
This feature gives the option to regulate each role's message composing permissions.
Check the corresponding boxes for desired permissions.
Permissions are assigned on a role-by-role basis. For instance, to prevent a student from sending a message to "All Participants", un-check the Student Permission box located next to the option, "Allow the 'All Participants' options to the 'To' field."
Note: These options will be visible when clicking the "To" text box in Compose a Message, within the Message tool.