The setting is in: Administration Center > Features > Sales.
Notify people listed in the following groups defines what user group will receive emails about deals in the system that are not closed even though ther planned end is overdue. This is important because the notification should be delivered to responsible persons. You never lose an overview of deals that should be closed.
Click Notify people listed in the following groups to see the setting options.
Just mark groups that should receive the notification. For more information, see Groups.
When you change the settings, be sure to click Save. For more information, go to Features.