For each account (both customer or reseller ones) you can define the set of events for which e-mail notifications are sent to an account owner or unsubscribe it from the event notifications at all. To this effect, go to the Account Director - Customer Manager (for customer accounts) or to the Reseller Manager (for reseller accounts). Select an account and then select the Notifications tab.
In addition, you can define the set of events a customer can enable or disable e-mail notifications for using the Control Panel. This can be done per event, in the Configuration Director - Event Manager - Events, select an event, select the General Settings tab within an event settings and check or clear the Customer can control receiving notifications for this event box to allow or disallow customers to disable/enable receiving notifications about an event.