Re: Is Hotmail in the habit of ignoring MX records?

[Mark Andrews <marka () isc org>]

In message <25F0B21A-0319-45E3-9DBF-9906CB77AC6C () kapu net>, Michael J Wise writ
es:
> On Jul 27, 2012, at 6:40 PM, David Miller wrote:
>
> > MX records don't "chain".
>
> But they do, "Expand".
> And I can think of a way whereby if an MX record referenced itself, =
> *AND* included something extra =85 (did you see the something extra?)
>
> That it would be possible (and I'm not saying this is what is happening, =
> but =85 it could be) =85
> That an internal process could go resolving MX records, and adds them =
> all to an internal table, until it figures it's got 'em all=85
>
>       "Gotta Get 'Em All!"
>
> =85 and maybe, just maybe =85 it exhausts the table space, and gives up, =
> and tries the A record.
>
> I'm not saying this would be "Standard".

It would be broken.  MX records say which machines are set up to receive
email for a domain.  Delivering it elsewhere, unless explicitly overridden
(e.g. smarthost), is a security flaw in the MTA.

> I'm not saying this is the best, or perhaps even an acceptable way to do =
> it.
> Or that it is in fact what is happening.
>
> But the config looked weird, and I can imagine =85 a system being =
> written as described =85 and breaking just this way given that MX =
> configuration.
> I can imagine Test =85 not catching it.
>
> Aloha,
> Michael.
> --=20
> "Please have your Internet License            =20
>  and Usenet Registration handy..."
-- 
Mark Andrews, ISC
1 Seymour St., Dundas Valley, NSW 2117, Australia
PHONE: +61 2 9871 4742                 INTERNET: marka () isc org