In message <b59a4092-ce2f-44e4-84f9-77c18493a...@kapu.net>, Michael J Wise writ es: > > On Jul 26, 2012, at 6:34 PM, Mark Andrews wrote: > > > In message <a9a5c64b-831d-42bf-8a38-56cc3b9ba...@kapu.net>, Michael J = > Wise writ > > es: > >>=20 > >> On Jul 26, 2012, at 1:35 AM, Lou Katz wrote: > >>=20 > >>> The domain is cookephoto.com > >>=20 > >> Why does mail.metron.com have MX records? > >=20 > > Why do you care? There is nothing wrong with having explict MX > > records and they generally take up less room in a DNS cache then > > the negative response does especially if it is DNSSEC signed. > >=20 > >> And they're different. > >=20 > > Again why do you care? > > Why do *I* care? > I don't. > > I'm just trying to find the weird bit that maybe is causing hotmail to = > stumble. > And maybe an endless loop for an MX lookup might be what is causing = > hotmail to panic and throw out the MX records.
You don't lookup MX records for MX targets. This is basic MTA processing. If the MX lookup fails, as apposed to returns nodata, you don't lookup the A/AAAA records and synthesis a MX record. You treat it as a soft error and queue for retry later. Again this is basic MTA processing. You don't depend on ALL (ANY) returning MX records as they may not be in the cache. You need to make a explict MX query you get no MX records are returned in response to a ALL query. Mark -- Mark Andrews, ISC 1 Seymour St., Dundas Valley, NSW 2117, Australia PHONE: +61 2 9871 4742 INTERNET: ma...@isc.org
