I would love to see them support TLDs such as .dk, .de, .it etc. That way both me and my clients could begin consolidating domain registration in one place, instead of using expensive and shitty domain registration management services. Harder ones, like Tonga (.to) or Greenland (.gl) would be nice to have as well, but I don't think it's feasible (or possible even) to integrate with all countries.
Could it be I'm using an alias of Cloudflare@mydomain.industries?
Edit: Attempting "cf@domain.industries" and receiving the same error. Assuming you're accepting .industries registrations, it could very well be my corporate firewall blocking requests to something. I'll attempt again this evening from home.