On Thu, Jan 05, 2017 at 05:29:44AM -0700, Daniel Margolis wrote:
> > - For the case of an internationalized domain name, the "mx" field should
> > include domain patterns in their U form (e.g. "*.ñaca.com
> > <http://xn--aca-6ma.com>"), A form
> > ("*.*.xn--aca-6ma.com"), or both can be present?
> >
>
> I suppose this is underspecified in the draft!
>
> I would say based on https://tools.ietf.org/html/rfc6125#section-6.4.2 that
> it makes the most sense for this to be in the A-form, since otherwise the
> MTA would have to convert to the A form for checking. What do you think?
For domains that actually have MX records (not just implicit "domain.
IN MX 0 domain.") the MX records will already be in A-label form,
since they're the result of a DNS lookup. Nobody should have to
convert these to U-labels just in case the domain owner's STS policy
uses unicode.
Since domains for domains that actually receive email (not just
parked) lack of MX records is the exception and not the rule, the
same should apply to the implicit MX. In any case the name needs
to be converted to A-label form in order to perform the lookup
that determines that there are no MX records.
So, bottom line, for simple and deterministic behaviour the mx
property must be in A-label (ASCII) form, the client must compare
A-label names against this property, and U-label forms, should not
match.
--
Viktor.
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