Default email app's notification is disabled on Samsung Galaxy S4 In my Samsung Galaxy S4, under Applications Manager, the email app has its notifications turned off by default. 

This is stopping me from knowing when any of my emails come in. How can I turn this on?

I have found that others have the same issue but have not found a fix for this yet. The other people just changed apps to K9 email.
I had the same problem and this is what I did...
Start at your home screen and swipe down from the top to display your notifications. At the top right, tap the gear/wheel (which is settings). Then, tap accounts. Next, email. If you have more than one email on this app, you have to do the following for each email address--I have two on mine.

You will have a screen that has an accounts heading and common settings heading. Tap settings, then, on the next screen, tap the email you would like to adjust. Sync settings will come up. check the email notifications box and then select a ring tone that won't make you crazy every time you hear it! lol! And that should do it! 

p.s. you can also change your signature here as well, to personalize your outgoing messages by tapping signature and turning that function on..  :)