Hi David, where are you opening the links ''from?'' If this is a new problem in '''Outlook 365''' -- the locally installed Outlook program that is part of Office 365/Microsoft 365 -- there is a setting you need to change ''within Outlook'' to solve it: Go into File > Options and tell Outlook to use your default browser instead of Edge: <blockquote><img src="https://assets-prod.sumo.prod.webservices.mozgcp.net/media/uploads/images/2023-08-10-11-54-52-aaf833.png"></blockquote> Does that work on yours? Of course, that assumes Firefox ''is'' your default browser on Windows. If that is the problem: [[How to change your default browser to Firefox on Windows]].