Problem

Currently the email validator treats the complete address as a IDN Label. as a result it will fail fore every address that:

contains a substring longer than 63 characters and doesn't contain dots

For example: "12345678901234567890123456789012345678901234567890123456@example.com" (56 characters local-part; 11 characters domain part)

Possible Solution

split into local-part and domain-part and transform the parts independently.

Side-Note (if there have to be limits to the length of the address)

SMTP defines a set of limits for parts of an address that the validator should be able to handle:
local parts: 64 octets (should translate to 54 chars)
domain part: 255 octets (should translate to 255 chars)