On Mon, Apr 27, 2015 at 04:46:25PM +0100, Jeremy Harris wrote:
> > In other words any such encoding is a local matter, and can be
> > applied only at the system responsible for the domain.
>
> Sorry, but you have not justified this - only stated it.
> An MSA _is_ a local matter. It acts on behalf of a
> (possibly naive) MUA and is responsible for fixing up
> much unfortunate behaviour.
All I can say is:
* The syntax and interpretation of of the localpart of the
email address has always been and remains a local matter for
the domain specified as the domain part of the address. No
other domain can make any general assumptions about valid
alternative forms, ... EAI does not change this.
* MSAs are free to muck about with sender addresses, but need
to leave recipient addresses in remote domains alone. The
syntax of those addresses is only known to the receiving
domains.
* There is certainly no expecation that remote domains will
do anything useful with "xn--<Punycode>" variants of UTF-8
addresses. If the sender used a UTF-8 (localpart) recipient
address, but the nexthop domain does not support SMTPUTF8,
the mail needs to bounce.
I think this is pretty clear from John's post, and I rather think
that what needs justification is performing the encoding, not advice
to avoid it.
On what basis is encoding localparts in remote domains a reasonable
transformation that an MTA or MSA might apply? When might Exim
apply it?
--
Viktor.
