Mail push notifications missing after iOS 11 upgrade

Ever since upgrading to iOS 11 the users are facing issue with their mail push functionality of iphone. Only get Mail push notifications when in Mail or the Home screen but never on lock screen or while phone in sleep mode.  Otherwise all queued up messages will only appear when user opens up the Mail. The issue is seen on both my iPhone and iPad. Even the latest models of iphone 7 and 7+ have this mail push notification issue. Toggling/changing settings IS NOT WORKING. The iOS update has definitively caused settings to not work on the phone, and it has disrupted how certain apps function as well.
Below are few fixes for : iphone 7 mail push not working in  iOS 11

Make sure that  you have following setting enabled that, go to Settings --> Mail --> Notifications --> here is where you will select the account(s) that you want to enable the feature (you have to do it one account at a time), after selecting the account toggle on Show on Lock Screen to show your emails on the Lock Screen, you can also enable Show in History so when you are on the Lock Screen and swipe up it will retain your emails there until you open the mail app.

Fix 1: Check your mail server

Push is only supported by iCloud and Microsoft Exchange with the built in mail app, as it requires cooperation from the mail server. Yahoo and gmail support Push, but only with their own apps, not with the built in app.

To push and fetch for outlook in iOS 11. Go to Settings—> accounts and passwords—>fetch new data then select your mailbox and check mark for fetch or push.

For paid Google G-suite accounts you need to install a Apple Push Certificate and enable Device Management - as well as set up the account as an Exchange account (not a Google account) on devices.

With all that in place (and notifications enabled for the account) you'll get push email an the relevant notifications.

Fix 2 : Wait for some time

Since Push for iCloud.com email stopped working on both my iPhone or iPad, Its quite possible that it's not a device problem. It is observe that both type of devices stopped working at the same time without changing any settings.

For many users the iCloud email account is Pushing again to my iOS devices. The users claimes that they didn't change a thing, didn't reboot,  just like last time for them, it just stopped working for a few weeks after the new iOS release, then magically started working again