Turn off the voice notification for emails on GALAXY S4?
If this is happening to you, you might be in Driving Mode.  You might have not actually switched to Driving Mode physically, but if you've paired (Bluetooth) with you're vehicle, it may automatically switch to Driving mode when you enter the car.  

Pull down the notification bar from the top of the screen. If Driving Mode isn't one of the five icons at the top of the screen hit the icon that looks like three little boxes and one set of arrows.

That should open a big list of toggle switches. Look for driving mode and see if it is turned on/lit up. If it is turn it off and the voice notifications should stop.