Add mail account to iphone 4 using iOS 6 and El capitan

I have an iPhone 4 using iOS 6 which has had severe battery drain for the past week or so.

To fix this ive attempted to remove all mail accounts on my phone with the intention of adding these back via itunes - which I believe I did in Mountain Lion.

Now there is no option for mail in itunes to add mail accounts - where has this gone? Do i need to manually add each email account?