Re: UUCP, etc., and SMTP/822/MIME mail (was: Re: I-D ACTION:draft-hoffman-utf8headers-00.txt)

> > at the time we were working on what became RFC 1342 we
> > realized that a single header field to tag the charset used
> > throughout the header would not be sufficient, because
> > different parts of the header are generated by different
> > agents on different machines.   one of the reasons for 1342
> > was to be able to encode such things in ASCII, but another
> > reason was to be able to tag each bit of human-readable text
> > with a separate charset.  what we might be finding out is that
> > it's not reasonable to expect everyone to use utf-8, and that
> > we're going to continue to need to deal with multiple charsets
> > (though perhaps fewer than are in use now) perhaps including
> > different charsets in different parts of the message header.
> 
> Keith, while I agreed with (and strongly supported) that 
> reasoning at the time, in the ensuing eleven or so years Unicode 
> (and maybe UTF-8) have achieved sufficient adoption that it 
> might now be reasonable to say "systems injecting non-ASCII 
> characters into header fields or equivalent contexts are 
> required to take responsibility for converting to UTF-8"... 

that's onerous but more-or-less doable.  what doesn't seem doable is
to prevent subsequent systems that handle the message (or reply
to it) from adding their own, non-utf-8, header contents.