> On May 4, 2021, at 2:48 PM, admin--- via Exim-dev <exim-dev@???> wrote:
>
> https://bugs.exim.org/show_bug.cgi?id=2730
>
>
> RFC 6531 says you SHOULD do this. In IETF-ese "SHOULD" means MUST unless there
> is a compelling technical reason not to do it, not do this if you feel like it.
> (That's MAY.)
>
> It's not a huge bug but it looks easy to fix.
It seems you're referring to:
https://tools.ietf.org/html/rfc6531#section-3.7.3
When an SMTPUTF8-aware SMTP server adds a trace field to a message
that was or will be transmitted with the SMTPUTF8 parameter included
in the MAIL commands, that server SHOULD use the U-label form for
internationalized domain names in the new trace field.
Which appears to be concerned primarily with the "Return-Path:" header,
which is only added on *final* delivery to a mailbox (possibly via
LMTP).
In that context, use of non-ASCII domain forms may needlessly break
message delivery, if the mailstore does not support non-ASCII headers,
and UTF8 would not otherwise appear in the message headers.
Also "Return-Paths" in UTF8 form would rather hinder abuse reporting,
or other help from postmasters, ... when the script in question is
foreign to the mail system operators. Users, on the other hand, rarely
look at trace headers...
Thus section 3.7.3 of the RFC looks misguided to me, I would would be
tempted to ignore it with prejudice.
--
Viktor.
