This property is used to configure whether or not emails should be sent for a particular event.
The default value is FALSE so an email is not sent.
The <event_name> component of the property name can be
one of the Event Types.
The default option available in most of the other
event email properties is not valid.
Most of the event email properties allow you to specify a default value for all Event Types.
This does not make sense for this particular property, and so is not available.
Please see the overview of Event Mails for usage examples.