[dathinab]

> Punycode [...] and the local-part was still limited to ASCII.

the funny part is this is only half true

The true part: Punycode has never be standardized for the localpart and as such taking a email address with non us-ascii characters in the local part and punycode encoding it is fundamentally wrong.

But: Nothing prevents you to have a local part which "happens" to look like punycode and especially in the early SMTPUTF8 days many providers which did allow non-us-ascii email local parts automatically created an "alias" email address where the local part was punycode encoded. Nothing in the standard prevents this and as consequence punycode encoding a local part _might_ just happen to work for some subset of non-us-ascii emails.