the native client always connects to the web client that was started last. if a user has the same outlook account opened in different browsers or a browser and the desktop client, it's not obvious which instance is actually communicating with the native client.

given that this could also indicate a takeover attempt, this should not happen automatically. instead, the currently connected web client should warn the user that another instance is trying to connect and ask for permission. the second web client therefore should inform the user that the native client is currently connected elsewhere and must wait for that connection to end.