--On Friday, December 17, 2010 18:42 -0500 John R Levine
For simplicity one might try them in the order returned by
the resolver, for example: Walk through the answer section
and, if A, use AF_INET; if AAAA, use AF_INET6.
An MX lookup just returns the name of the MX. There might be
A and AAAA records in the additional section, but there also
might not, and as I understand it, the order of records in a
section of a DNS response has always been considered to be
arbitrary. So I agree, these tea leaves aren't worth reading.
And that, of course, is exactly why the relevant section of 5321
carefully avoids saying anything specific or normative about
order of attempts.