> On Jul 23, 2014, at 9:46 AM, Tony Finch <d...@dotat.at> wrote: > > Hector Santos <hsan...@isdg.net> wrote: >> >> What has been crossing my mind regarding this NULL MX setup, was the possible >> privacy issue with NULL MX root domain "Traceability" aspect with legacy MTAs >> performing SMTP "Implicit MX" (No MX record, Fallback to A record) logic. >> What will the A query IP resolved to when the exchange points to the root? > > Null MX records suppress fallback-to-A. The target "." does not have any A > records. http://www.ietf.org/mail-archive/web/dnsop/current/msg12153.html
So by "suppress" you mean, for the vast wide field of "Null MX" ignorant MTAs, a positive return of a MX record with a preference of zero, a blind A lookup of "." returns an 0 ip value and this causes an inherent cancellation, "suppression" of the outbound attempt? I can understand how a supportive MTA can leverage it, but I was thinking what the impact might be for the legacy MTA. Not all DNS resolvers return the expansion depending on the API and the caching servers in play. -- Hector Santos http://www.santronics.com _______________________________________________ DNSOP mailing list DNSOP@ietf.org https://www.ietf.org/mailman/listinfo/dnsop
