Hi, there is a reasonable chance that Windows is sending the link from Outlook to a different Firefox profile, and possibly even a different Firefox installation. If you could do a little research on the Troubleshooting Information page, that would be helpful. In each window -- the normal one and the one Windows thinks is the default URL handler -- open that page using either: * "3-bar" menu button > "?" Help > Troubleshooting Information * (menu bar) Help > Troubleshooting Information * type or paste '''about:support''' in the address bar and press Enter In the first table on the page, under the heading Application Basic, compare these lines: (A) Profile Folder -- this shows the settings folder being used in that session of Firefox; focus on the last part of the path with 8 random characters followed by a . followed by the familiar name (B) Application Binary -- this shows the path from which Firefox itself was launched, which commonly would be one of these but could be anywhere if there's a custom install * C:\Program Files\Mozilla Firefox * C:\Program Files (x86)\Mozilla Firefox If you have a dual install, we should plan carefully to fix the Windows settings without breaking other applications, so please don't rush to delete any folders.