There is a group of enterprise users who have been added to sourcing events as observers, these users do not have any role assigned to them. The users have been receiving multiple event notifications and they do not have an option to disable the notifications. The "Change Notification Preferences" option is not available in the menu.
How can they disable event notifications? We cannot assign them specific roles as that would give them option to search and access other events.
Do you have them added as Active Observers? If so, then they will get all the same notifications as the buyer running the event. Try using the "Observer" or create a group with the role: "Team Member with Limited Access". Run a test, create an event, add a user to each of the groups and see the difference in the messages they receive.