I apologise at the outset if I'm raising a hoary issue. I can see from web searches others have had it - I haven't found an instance where anyone has solved it. I've tried to look in posts to this forum for an answer, but the search function doesn't help me, and I don't have time to scroll through 290+ pages. If a moderator can point me where to go, I'd be very grateful.
Just to confirm the issue: I have Opera Mail as my email app on a new (to me) Asus laptop. I am very happy with it in itself, but cannot find a way to set it as my default email app (so that I can right-click an item and raise a new email message, with whatever I've right-clicked as an attachment or inclusion).
I think the problem is essentially a Microsoft one, in that (a) Win 10 is poorly designed, or deliberately restrictive, as compared to all earlier Windows versions, in respect of setting default apps for file types and (b) this is compounded by their not including (? excluding) Opera Mail as an 'option' in the set default process that is offered.
Here's hoping there IS a solution or work round .....?