Re: [dmarc-ietf] Ticket #111 - MX/A/AAAA test needs justification

"Murray S. Kucherawy" <superuser@gmail.com> Fri, 07 May 2021 19:06 UTC

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From: "Murray S. Kucherawy" <superuser@gmail.com>
Date: Fri, 7 May 2021 12:06:16 -0700
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To: Douglas Foster <dougfoster.emailstandards@gmail.com>
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Subject: Re: [dmarc-ietf] Ticket #111 - MX/A/AAAA test needs justification
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On Thu, May 6, 2021 at 5:02 PM Douglas Foster <
dougfoster.emailstandards@gmail.com> wrote:

> I have begun data collection on the effectiveness of the MX and A tests.
>  Wildcard DNS entries increase the frequency of false positives and reduce
> the usability of the test.   For example, "msaqq189.ford.com" returns a
> set of MX results, but I rather doubt that I made a lucky guess and found a
> mail domain that Ford Motor actually uses.
>

There's no need to guess.  You can query for wildcard records:

$ host -t mx '*.ford.com'
*.ford.com mail is handled by 10 cluster4.us.messagelabs.com.
*.ford.com mail is handled by 20 cluster4a.us.messagelabs.com.

-MSK