https://www.theverge.com/2018/6/15/17467700/google-gmail-push-notifications-machine-learning-ai

Google wants to help you cut down on the notification noise by using AI to prioritize Gmail push notifications.

The app now uses machine learning to recognize and filter the messages you may want to read over the ones you don’t, and it will only send you a push notification if the app believes it’s important to you. The update is available for some iOS users in the Gmail app (ahead of the Android version).