On Mon, Apr 27, 2015 at 10:57:02AM +0100, Jeremy Harris wrote:
[ I don't know whether John Klensin remains subscribed to the
list, so I'll chime in with my response, with any luck John will
correct any mistakes I might have made. ]
> On 24/04/15 21:15, John C Klensin wrote:
> > Just don't try to encode local parts. Really. You will
> > hurt the sites and systems that support non-ASCII addresses and
> > headers all the way to the client desktop and won't really help
> > those who don't.
>
> Are you speaking to pure MTAs here, or also MSAs? MUAs?
>
> > Exim, as an MTA
>
> Exim can also be an MSA.
Neither MTAs nor MSAs should attempt to apply Punycode encoding to
UTF-8 EAI email address localparts. The only acceptable alternative
representation that comes to mind is a table of ascii-only addresses
explicitly configured for senders in the MSA's local domains, that
are accepted on the reverse path as valid addresses for these same
senders. With that, you could encode sender addresses when forwarding
ascii-only recipients to non-EAI systems (or sending email to
recipients in the same domains for which ascii-only forms exist).
In other words any such encoding is a local matter, and can be
applied only at the system responsible for the domain.
--
Viktor.
