Wietse Venema via Postfix-users:
> John R. Levine via Postfix-users:
> > On Thu, 2 Jul 2026, Danjel Jungersen wrote:
> > >> That's an Internationalized Domain Name (IDN), in the Unicode U-label
> > >> form.
> > >> THe encoded A-label equivalent which you can look up in the DNS is
> > >> xn--vestskovslbet-knb.dk
> > >> ...
> > >> A possible workaround is to send mail to the A-label version of the
> > >> address, [email protected] which would not need SMTPUTF8.
> > >> I poked at the server and it accepted that address.
> > >
> > > Is there a reason why this is not attempted automatically?
> >
> > Postfix considers the A-label and U-label versions of the address to be
> > distinct. Wietse might tell us what the thinking was.
>
> The thinking was that Postfix would not automatically convert between
> one form and the other a) when searching a table and b) when
> generating an indexed table from a text file. There are very mundane
> reasons for the latter - the postmap command does not know whether
> something is a localpart (not covered by IDN) or a domain name
> (covered by IDN).
... whether something without an @....
Wietse
> > > The receiver claims that he receives mail from other people using the IDN
> > > version.
> >
> > Honestly, I'm sceptical. My guess is that the other people have the
> > A-label version of the address in their address book, and his mail program
> > doesn't show him the address in incoming mail.
> >
> > I have done a lot of EAI related work for ICANN and I can tell you that
> > using IDN mail addresses is one of those things that is supposed to work
> > but is painful in practice. A lot of software almost but not quite
> > implements it, as we saw here. Postfix support is fine (one of the things
> > I did was to test it and it got a gold star) but you have to turn it on.
>
> Ack.
>
> Wietse
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