In message <[email protected]>, Douglas Otis
writes:
>
> On Apr 11, 2009, at 4:25 AM, Florian Weimer wrote:
>
> >> The MX RR will be ignored. There will be an AAAA DNS request and a
> >> fallback to the A RR for security.eu.debian.org. Newer versions of
> >> sendmail and Postfix will treat that MX RR as a bad MX and reject
> >> the message instead of retrying.
> >
> > Exim also treats the record as a "no SMTP service here" indication.
> > I would even go so far to call this a de-facto standard (which just
> > hasn't been documented by the IETF).
>
> It would incorrect to describe MX records targeting the root as being
> a widely adopted standard to signal "No SMTP Service".
>
> In the past, Paul Vixie raised concerns about even using root targets
> within SRV records, which has always been defined as a means to signal
> no service. He said that his experience at the root had shown
> programmers should not be trusted to properly recognize root domains
> within SRV records. In the case of SMTP, there was never a standard
> to properly ignore root targets. A signaling scheme that shifts the
> signaling of no SMTP service responses to the root may prove
> detrimental.
If a application is doing the wrong thing w.r.t. SRV records
then fix the application. The root servers can handle a A
and AAAA queries for ".". Most cache's will correctly
negatively cache such responses.
As for "MX 0 ." the sooner this gets defined as no SMTP
service for this domain the better. The cost for changing
this is only every going to increase.
Mark
> -Doug
>
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--
Mark Andrews, ISC
1 Seymour St., Dundas Valley, NSW 2117, Australia
PHONE: +61 2 9871 4742 INTERNET: [email protected]
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