Re: [spfbis] RFC7208 4.6.4 Interpretation - MX Lookup Count Inconsistencies

[Tim Wicinski <[e-mail]>]

I am always happy when I'm proven wrong. Thanks Mr. John.

tim

On Sun, Jan 22, 2023 at 10:13 PM John Levine <[e-mail]> wrote:

> It appears that Tim Wicinski  <[e-mail]> said:
> >I also feel that technology stacks have matured over time.  Jan, do you
> see
> >real world examples of a domain with 11 MX servers?
>
> Well, there's Comcast:
>
> $ host -t mx comcast.net
> comcast.net mail is handled by 50 mx1a1.comcast.net.
> comcast.net mail is handled by 5 mx2.mxge.comcast.net.
> comcast.net mail is handled by 50 mx2a1.comcast.net.
> comcast.net mail is handled by 50 mx1c1.comcast.net.
> comcast.net mail is handled by 5 mx1.mxge.comcast.net.
> comcast.net mail is handled by 50 mx2c1.comcast.net.
> comcast.net mail is handled by 50 mx1h1.comcast.net.
> comcast.net mail is handled by 50 mx2h1.comcast.net.
>
> And there's Yahoo, but its MX is only four lookups:
>
> $ host -t mx yahoo.com
> yahoo.com mail is handled by 1 mta6.am0.yahoodns.net.
> yahoo.com mail is handled by 1 mta7.am0.yahoodns.net.
> yahoo.com mail is handled by 1 mta5.am0.yahoodns.net.
>
> $ host mta5.am0.yahoodns.net.
> mta5.am0.yahoodns.net has address 67.195.228.109
> mta5.am0.yahoodns.net has address 98.136.96.76
> mta5.am0.yahoodns.net has address 67.195.204.72
> mta5.am0.yahoodns.net has address 67.195.204.79
> mta5.am0.yahoodns.net has address 67.195.228.111
> mta5.am0.yahoodns.net has address 98.136.96.77
> mta5.am0.yahoodns.net has address 67.195.228.110
> mta5.am0.yahoodns.net has address 98.136.96.91
> $ host mta6.am0.yahoodns.net.
> mta6.am0.yahoodns.net has address 67.195.204.74
> mta6.am0.yahoodns.net has address 98.136.96.76
> mta6.am0.yahoodns.net has address 67.195.228.110
> mta6.am0.yahoodns.net has address 67.195.204.79
> mta6.am0.yahoodns.net has address 67.195.204.77
> mta6.am0.yahoodns.net has address 67.195.228.111
> mta6.am0.yahoodns.net has address 67.195.228.94
> mta6.am0.yahoodns.net has address 98.136.96.77
> $ host mta7.am0.yahoodns.net.
> mta7.am0.yahoodns.net has address 67.195.204.79
> mta7.am0.yahoodns.net has address 67.195.204.77
> mta7.am0.yahoodns.net has address 98.136.96.91
> mta7.am0.yahoodns.net has address 67.195.228.111
> mta7.am0.yahoodns.net has address 67.195.228.106
> mta7.am0.yahoodns.net has address 67.195.228.94
> mta7.am0.yahoodns.net has address 67.195.204.72
> mta7.am0.yahoodns.net has address 98.136.96.77
>
> And Charter:
>
> $ host -t mx charter.com
> charter.com mail is handled by 10 nce.mail.chartercom.com.
> charter.com mail is handled by 10 ncw.mail.chartercom.com.
>
> $ host nce.mail.chartercom.com.
> nce.mail.chartercom.com has address 142.136.234.134
> nce.mail.chartercom.com has address 142.136.234.135
> nce.mail.chartercom.com has address 142.136.234.136
> nce.mail.chartercom.com has address 142.136.234.137
> nce.mail.chartercom.com has address 142.136.234.138
> nce.mail.chartercom.com has address 142.136.234.139
> nce.mail.chartercom.com has address 142.136.234.142
> nce.mail.chartercom.com has address 142.136.234.143
> nce.mail.chartercom.com has address 142.136.234.144
>
> $ host ncw.mail.chartercom.com.
> ncw.mail.chartercom.com has address 142.136.235.134
> ncw.mail.chartercom.com has address 142.136.235.135
> ncw.mail.chartercom.com has address 142.136.235.136
> ncw.mail.chartercom.com has address 142.136.235.137
> ncw.mail.chartercom.com has address 142.136.235.138
> ncw.mail.chartercom.com has address 142.136.235.139
> ncw.mail.chartercom.com has address 142.136.235.142
> ncw.mail.chartercom.com has address 142.136.235.143
> ncw.mail.chartercom.com has address 142.136.235.144
>
> I occasionally see spammy looking hosts with a lot
> of MX'es but if their SPF checks fail, who cares.
>
> R's,
> John
>