This hasn’t worked for a while now for newer devices.
I used to forward. Then I decided to try gmail. Now I use an app called email (link below). I love it. I don’t think I’ll ever go back. And the icon is very similar to stock, if that’s something that matters.
I still keep the stock mail app installed and have it set not to alert me. My reason for this is to allow me to respond to email links. Apple STILL hasn’t allowed us to pick a default. You either need the mail app installed or copy and paste. Much easier to just have the mail app installed.
https://itunes.apple.com/us/app/email-edison-mail/id922793622?mt=8