Re: [idn] IDNs in email message bodies

[Keith Moore]

> HELO, PATH, HTTP sequences and other "pushed" names can be ACE, or they
> can use an RFC-2047 style encoding syntax.

as far as I'm concerned, RFC 2047 encoding is a non-starter for domain names
in protocol elements.  2047 was specifically designed to encode text whose
only purpose was to be presented to a user; and it therefore completely 
skirts all issues related to normalization, canonicalization, etc.

(note that even if you use 2047 to encode nameprepped Unicode, there is 
more than one way to encode such names... names encoded in such a way
cannot be compared for equivalence as if they were ascii)

any domain name that appears in a protocol element that is intended to be 
*interpreted* or *compared* (as opposed to merely *displayed*) needs to 
be ACE-encoded.

Keith