Mail do not come automatically. It comes only when I open the Mail App

16 Dec
Software Issues

Go to Settings> Accounts and Passwords> Fetch New Data.

Scroll down and you will find options like Manually, Every 30 Mins etc.

You may select any option, Every 15 Minutes being the fastest.This will sync your mails in every 15 minutes automatically and hence you will be able to get your mails on time.