Hi Stephen, At 10:12 PM 2/18/2017, Stephen J. Turnbull wrote:
The problem that I thought we may face is internationalized mailboxes and domain names *are still ASCII* which encodes Unicode.
OK, I looked it up, and I was almost certainly wrong. The relevant RFCs are actually 6531 (SMTPUTF8 extension), 5890 (IDNA), and 3492 (Punycode). IDNA allows "U-labels" (UTF-8), which we can gracefully extend to, and "A-labels" (encoded using Punycode, which uses the ASCII repertoire). AFAICT (haven't really looked carefully), Punycode uses only letters, digits, and the hyphen ("-").
So I withdraw the comment.
RFC 5890 can be used for the domain name part. The issue would be about what to do for the local part. If I recall correctly, the question was not discussed as part of RFC 6531. I suggest taking a look at RFC 7564.
Regards, -sm