Invite a surface friend by email

Are there any options to invite a friend from the surface by email? I got a Deshrieked Mandrake and got its opportunity card but it had no option to invite someone. Is this only possible if you have a linked facebook or twitter account?

I tried inviting someone a couple months back through the game, remembering those options existed, but I couldn’t find any of them. I think they retired them for some reason.

There was a problem with the app, they’ll probably be reintroduced sometime after the android version comes out.