4 ms·

Great work, I put three basic rules in my comment and you failed two of them :)

• Avamander 5y ago
  Theoretically a MX record on a TLD is valid, but I doubt many try to use that.
  • Ekaros 5y ago
    Perversely it depends. With older and country TLDs yes, with the new ones no... I'm not even joking... This isn't RFC, but ICANN...
    • yakak 5y ago
      Indeed I couldn't find a brand TLD with an MX, but there does seem to be an MX on ua, so "support@ua" is a valid email with no "."..