How to turn off autocorrect for iPhone 6 Mail? Here's what I've tried: 


Open the “Settings” app on the iPhone  
Go to “General” and then to “Keyboard”
Locate “Auto-Correction” and flip the switch to OFF 


This disables autocorrect for all apps, with the exception of Mail

The emails are still being autocorrected. How should I turn off autocorrect for the iphone 6 default Mail application 

My IOS version is 10.3.2
Make sure you’re using the apple keyboard.
Since keyboard setting changes made in the Settings apps only apply to be built-in Apple keyboard, you’ll need to make sure that you’re using it. Touch and hold the globe key on your keyboard to change back to your Apple localized keyboard.
You could also disable autocorrect in the companion app for your custom keyboard, in your case the SwiftKey app.