IMac 2010 Sierra & Macbook Pro Catalina Hi, I have been dialoguing with Microsoft over the random behaviour of Outlook when I click on a message (or the command 'Open the message in a new window'). The window always opens but the message is not always displayed- there is no pattern in this behaviour. See enclosed screen captures. This problem occurs on my two machines (see above). I also have Safari and this problem does not occur with this browser. Microsoft thinks it's a Firefox problem ''....il s'agit d'un problème spécifique au navigateur...." Do you have any ideas? Do you want a copy of my exchange with Microsoft? Many thanks for your answers Best regards Jeremy Lees