digging into the logging folder on the exchange installation I found the folder
E:\Program Files\Microsoft\Exchange Server\V15\Logging\HttpProxy\Mapi
where I could find authentication events related to Outlook 2010 (Negotiate) and Outlook 2016 (Bearer).
But I cannot find the related authentication events from any other clients such as the Windows Mail client, Outlook mobile app or Mac clients. Does someone know where I could find those?
Many thanks.