Mark Sapiro writes:
That doesn't really address my question. That has to do with internationalized email addresses. Granted the listname must be a valid local part of an email address, but that doesn't mean every valid local part has to be a valid list name.
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.
Thanks for your work on this, Mark!
Steve