[dns-operations] creeping poorness of judgement

Paul Vixie paul at redbarn.org
Sat Mar 14 02:53:57 UTC 2020

Viktor Dukhovni wrote on 2020-03-13 18:48:
> On Sat, Mar 14, 2020 at 01:16:09AM +0000, Paul Vixie wrote:
>> ...
> But you don't actually have to hinder forwarding of your email by
> publishing SPF, another option is to use only IPv4 when sending email
> via google's MX hosts.  This can be done by hiding the AAAA records of
> the Google MTAs from Postfix (my below adaptation of the example uses
> the PCRE "x" option to make the filter more readable):
>      http://www.postfix.org/postconf.5.html#smtp_dns_reply_filter
>      /etc/postfix/main.cf:
>          pcre = pcre:${config_directory}/
>          smtp_dns_reply_filter = ${pcre}smtp_dns_reply_filter
>      /etc/postfix/smtp_dns_reply_filter:
>          # /domain ttl IN AAAA address/ action, all case-insensitive.
>          # Note: the domain name ends in ".".
>          /^\S+\.google\.com\. \s+ \S+ \s+ IN \s+ AAAA \s+/x IGNORE
>          /^\S+\.smtp\.goog\.  \s+ \S+ \s+ IN \s+ AAAA \s+/x IGNORE

that is delightfully unhinged, but i would sooner call joe abley on the 
phone then to put PCRE's into config files trying to filter out 
dig-format DNS records. thanks for the cackle, though.

P Vixie

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