In order to properly implement either push messaging or frequent polling themselves, an app needs to run a foreground service. This is displayed as a persistent notification. It will normally be marked as a silent notification - with the lowest possible priority, so it will be collapsed at the bottom and - won't show up as an icon in the status bar or on the lockscreen. A battery - optimization exception is also needed for the app to bypass device idle states - and run while the device is idle. If you can tolerate delays while the device - is idle, then the battery optimization exception isn't mandatory.
+ with the lowest possible default importance for a foreground service + (IMPORTANCE_LOW). It can be reduced to the lowest importance (IMPORTANCE_MIN) + by the user if they set the notification channel to be collapsed which will + collapse it in the notification tray and it won't show up as an icon in the + status bar or on the lockscreen anymore. A battery optimization exception is + also needed for the app to bypass device idle states and run while the device + is idle. If you can tolerate delays while the device is idle, then the battery + optimization exception isn't mandatory.FairEmail and Signal are examples of apps using the proper approach of a foreground service combined with an optional battery optimization exception.