[dns-operations] Why would an MTA issue an ANY query instead of an MX query?

[Kyle Creyts]

ANY queries, in my *limited* experience, have had higher latencies by an
order or two of magnitude. but that was mostly when I was doing open
resolver research a year or two ago.
On Jun 10, 2012 7:25 AM, "DTNX Postmaster" <postmaster at dtnx.net> wrote:

> On Jun 10, 2012, at 12:33, Dobbins, Roland wrote:
>
> > On Jun 10, 2012, at 5:29 PM, <sthaug at nethelp.no> wrote:
> >
> >> One word: qmail. Google "qmail dns any query".
> >
> > If that's it, then would asking djb to change its behavior so as to
> issue TXT requests to look for SPF records make sense?
> >
> > I know that doesn't do anything for currently-deployed MTAs, but one has
> to start somewhere . . .
>
> Asking DJB to change qmail behavior? ;-)
>
> It's not just qmail, though. I bet there's some engineers who consider
> it more efficient to do a single query to get all the data they want. A
> lot of the 'ANY' queries we get originate at Google, HE etcetera.
>
> Google is known to be obsessed with latency, for example, so I wouldn't
> be suprised if they deliberately request ANY and then parse and cache
> the results for a multitude of uses.
>
> A single ANY query for a domain gives you the NS, MX, TXT and SPF
> records, plus any A/AAAA record present. At scale, who knows, the
> reduction in number of queries probably adds up.
>
> And then there's the information harvesters, who query hosted domains
> in sequence. They actually seem to account for around 40% of our
> 'normal' ANY traffic with just a few IP addresses.
>
> Cya,
> Jona
>
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