On Wed, 26 Mar 2008, John C Klensin wrote: > > At the time 974 and 1123 were written, the only sort of address record > in Class=IN was an A RR, and those documents used "A RR" terminology. > The change in 2821bis essentially substituted the phrase "address > record" (or "address RR") for "A record" because (i) that seemed to be > consensus on the list at that time and (ii) there is significant, > although not universal, existing practice that is consistent with > treating IPv4 (A) and IPv6 (AAAA) RRs the same way, at least with regard > to SMTP. > > With that change to "address record", if no MX record is found, the SMTP > client is required to look for DNS names with either A or AAAA RRs, > rather than A RRs only. There's also RFC 3974 (Jan 2005, informational) which recommends treating AAAA like A. The most popular MTAs implement this logic. Tony. -- f.anthony.n.finch <dot@xxxxxxxx> http://dotat.at/ HUMBER: VARIABLE 3, BECOMING SOUTHERLY 4 OR 5. MODERATE. OCCASIONAL RAIN. MODERATE OR GOOD. _______________________________________________ IETF mailing list IETF@xxxxxxxx https://www.ietf.org/mailman/listinfo/ietf