Microsoft has introduced two versions of Outlook in Windows 11: Outlook Classic (a Win32 desktop application) and the New Outlook. Users have reported significant performance issues with the New Outlook, noting a lag of approximately 10 seconds for tasks that Outlook Classic performs instantly. The New Outlook operates on WebView2, which involves multiple processes and higher memory consumption, while Outlook Classic runs as a single process. Microsoft is aware of these performance challenges and is testing a new API called 'Delayed Message Timing' to address them. Users find Outlook Classic to be more reliable and faster, particularly for businesses that need efficient notification processing.