To enable a stream to send notification emails to a notification group, you have to set notifications for the stream, when to send the email, and to which notification group.
In the Streams View, on the same row of the solution under the Actions columns, click the More button. For more information, see Streams View.
Click Set Notifications.
In the Send email when pop-up window, check the stream event you want to be notified of and select the notification group from the drop-down menu to inform by email.
Click Apply.