Outlook features an embedded webview powered by Microsoft Edge.
When you click a link for a website, we keep you inside of Outlook so you can quickly find what you need and get back to your emails. This is intended to help your workflow without removing you from the in-app experience. You can even search right from inside this webview. If you need to jump to your browser app simply tap the overflow menu at the bottom and choose Open in Browser.
This feature is currently not available for users with a Microsoft 365 or Exchange email account.