In message <a65d48e6-b91a-477e-aad0-8777aa57e...@mail-abuse.org>, 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 > > _______________________________________________ > DNSOP mailing list > DNSOP@ietf.org > https://www.ietf.org/mailman/listinfo/dnsop -- Mark Andrews, ISC 1 Seymour St., Dundas Valley, NSW 2117, Australia PHONE: +61 2 9871 4742 INTERNET: mark_andr...@isc.org _______________________________________________ DNSOP mailing list DNSOP@ietf.org https://www.ietf.org/mailman/listinfo/dnsop