I dislike Microsoft as much as the next person, but AFAICT this is about opening the link inside Outlook, in a sidepane:
> ... browser links from the Outlook app will open in Microsoft Edge by default, right alongside the email they’re from in the Microsoft Edge sidebar pane.
Also the title has been editorialized here, the original title describes what is actually happening:
> Outlook emails open next to web links in Microsoft Edge
You can also turn it off:
> Ultimately though, if this experience isn't right for you, you can turn off this feature the first time it launches in Microsoft Edge, and then in Outlook settings at any time after that.