Outlook Mail links to be opened in Edge, regardless of the default browser
Redstone 5 build uses Microsoft Edge browser for opening email links
The current version of Windows 10 allows you to set a default browser for opening any web links you click on, but this may be about to change in the Fall 2018 update for Windows. A test RS5 build, available for Insiders in the Skip Ahead ring, uses the Edge browser for opening links in the Windows 10 Mail app, regardless of the default system browser. So, even if you set Chrome as a default browser from Settings, Edge will open the links from the Mail app. Microsoft says that Edge provides the most secure experience on Windows 10:
For Windows Insiders in the Skip Ahead ring, we will begin testing a change where links clicked on within the Windows Mail app will open in Microsoft Edge, which provides the best, most secure and consistent experience on Windows 10 and across your devices. With built-in features for reading, note-taking, Cortana integration, and easy access to services such as SharePoint and OneDrive, Microsoft Edge enables you to be more productive, organized and creative without sacrificing your battery life or security. As always, we look forward to feedback from our WIP community.
Microsoft’s decision has already faced negative reactions from the press, but the impact on the user experience may be far less significant that expected. There is also possible that setting Edge as a default browser in the Mail app is temporary and only for testing purposes. But one is sure, Microsoft is starting to push and promote Edge more prominently. Recently, an update to the Store app introduced a special section for Edge extensions.