How to Stop New Email Notifications in iOS 9
If new email messages appear on your lock screen or at the top of the screen in iPhone or iPad, then you can disable it by following the simple steps outlined below:
First, from your iOS 9 device, go to Settings -> Notifications -> Mail.
Say you are using Gmail, Apple iCloud, Yahoo! or any other email provider – all the email accounts will be listed on this Mail page. What you have to do is select any email account and then make changes as you like.
This way you can permanently stop email notifications.