2.2.21 [W3C-HTML52] Section 220.127.116.11.5. E-mail state (type=email)
C0039: Punycode in a value is not properly converted to IDN
The specification states:
18.104.22.168.5 E-mail state (type=email) ... User agents may transform the values for display and editing. User agents should convert punycode in the domain labels of the value to Internationalized Domain Names in the display, and vice versa.
Punycode in a value is not properly converted to IDN.