Globally for all events: wrapper.event.default.email.smtp.host property, or
For a specific event: wrapper.event.<event_name>.email.smtp.host property.
The "<event_name>" component of the property name can be
either the keyword "default",
or one of the Event Types.
By setting the default property,
all Event Types which are not set explicitly will take on that value.
This property does not have a default value.
Either the default or event type specific property must be set for emails to be sent.