Android phones have a different architecture for handling background execution of applications, which evolves with every new Android version.
Android processes applications running in the background and those running in foreground separately. But this causes quick draining out of the battery of Android phones. In the earlier versions of Android, there were no restrictions on the applications running in the background.
With the later versions, Android has the capability to stop applications from running in the background so that resource and memory usage is based on the need.
Until MiCollab 8.1.x, Android clients were using the exception Ignore Battery Optimization with the user's permission for receiving events from MiCollab server. However, with MiCollab 9.0 onwards, the Android client, in compliance with Google recommendations, drops the Ignore Battery Optimization exception and runs the FCM Push Notifications to keep receiving events from MiCollab server. This way, MiCollab Android client can receive events even when an application is not running, which was not possible with the earlier MiCollab 8.1.x clients.