I currently use Opera as my main browser. But if I click on any "mail to" links, it automatically opens Apple's Mail (which I don't use). My main mail server is Outlook (my university account). How do I change the default setting? I've looked through the settings/preferences and I can't see it

Minimise Button - haven't seen this problem raised on this forum. I'm using a (quite old) Macbook Air running Big Sur 11.01. Opera keeps losing the minimise button. I think it might be after I've used the "full screen" command. When I go back to normal screen, there's just a grey circle where there should be an amber button. Anyone got any ideas???