MailTo links do not open Outlook

When clicking on a mailto link, Outlook used to get opened and I could write my email. Now, when I click on a mailto link, it brings up the Gmail webpage while I don’t even have a Gmail account.

I’ve already made sure that Outlook has been set as my default mail client in Windows, but mailto links still bring me to Gmail.

How can I get mailto links to open with Outlook again?