In message <201303180038.r2i0cwet026...@calcite.rhyolite.com>, Vernon Schryver writes: > > 20741, so direct SPF RR hits is about one third of those using TXT RR, > > small, but, insignificant? I wouldn't really say so, but some might. I > > suspect the SPF wanting to be deprecated is because of the lack of > > take-up, due to lazy admins, there are some resolvers in use from > > ancient debian boxes that are so old, they dont understand the SPF RR, > > yes I know, they have bigger problems than that, but, again, comes down > > to laziness, DNS is not rocket science, I'm sure given ARM and access to > > google, a 13yo kid could get at least the "basics" right. > > Laziness?--nonsense. Postel's Law and simple logic predict the > deprecating of the SPF type as well as the continued practice of > publishing only TXT records by those with rational reasons to publish > SPF data. > > 1. SMTP servers (mail receivers) that have wanted to honor SPF -all > been forced to look for for SPF data in TXT records since the > beginning. There have been far more TXT records with SPF data > than SPF records. Therefore, the best course for SMTP servers > has been to request TXT and only request SPF if the TXT request > gives NODATA. Requesting both SPF and TXT types would cost extra > bandwidth and raise questions about what to do if both are present > and differ. Occassional differences between SPF and TXT are > inevitable due to caching in recursive resolvers even when the > authoritative server always changes both simultaneously.
Yet libspf2 requests SPF records and falls back to TXT on NODATA. It does not do a TXT query if it gets a SPF response. > 2. Rational operators of SMTP clients (mail senders) know that well > maintained SMTP servers understand #1 and so request TXT first or > request neither SPF nor TXT. > Publishing only SPF type records would double an SMTP client's > DNS costs. > Pubishing both SPF and TXT would not help well mantained SMTP > servers, but cost maintenance complexity and so potential errors. > Therefore, it is best to publish only TXT for well maintained > SMTP servers. > Badly maintained SMTP servers are likely to only check TXT records. The rational course would be to set a sunset date on TXT style spf records. April 2016 looks like a good date. 10 years after RFC 4408 was published. > Unlike the situations with IPv6 and DNSSEC, there are only costs > and no benefits for rational operators SMTP clients or servers to > change those two tactics. > > Those interested in wider perspectives about SPF and TXT RRs than any > single domain or the perceptions of SPF enthusiasts might consider the > tables reporting surveys in RFC 6686. One can ignore everything > specifically about SenderID and read only about popularity of SPF and > TXT records. https://www.rfc-editor.org/rfc/rfc6686.txt > > > Vernon Schryver v...@rhyolite.com > _______________________________________________ > Please visit https://lists.isc.org/mailman/listinfo/bind-users to unsubscribe > from this list > > bind-users mailing list > bind-users@lists.isc.org > https://lists.isc.org/mailman/listinfo/bind-users -- Mark Andrews, ISC 1 Seymour St., Dundas Valley, NSW 2117, Australia PHONE: +61 2 9871 4742 INTERNET: ma...@isc.org _______________________________________________ Please visit https://lists.isc.org/mailman/listinfo/bind-users to unsubscribe from this list bind-users mailing list bind-users@lists.isc.org https://lists.isc.org/mailman/listinfo/bind-users
