Microsoft might be planning to allow users to select 3rd party browsers to open external links. Following a change a few months ago, said to be for security reasons, users could only open the external links in Microsoft Edge. However, this is set to change as Microsoft will soon allow users to open external links in third-party browsers.
The Redstone 5 update released back in March forced Windows Insiders to open the external links in Microsoft Edge. Since then, people have filed feedback with Microsoft not to force them to use Microsoft Edge. The upcoming Mail and Calendar app update will have a Links option under Reading Pane which will allow users to choose if they want the links to open through Microsoft Edge or some other third-party browser.
Recently, Microsoft also announced Inking capabilities for Mail app as well. Microsoft has been working hard to shape these apps according to the feedback from the users. So while we wait for Microsoft to push this update, if you have any feedback then head to the Feedback Hub and send it to Microsoft.