The user can subscribe/unsubscribe to event types and decide through which delivery media notifications should be sent for each type.
If the event type supports public subscribers, users with the appropriate permissions can manually subscribe to it.
For each event type the user can enable/disable the delivery media available for the type. If a delivery media is disabled, when an Event in which the user should be notified occurs, no notification will be received through the disabled delivery media. If all delivery media are disabled no notification will be received by the user.