[BlueOnyx:21590] 550-5.7.1 this message does not meet IPv6 sending guidelines regarding PTR

[Lewis Gardner]

On a 5209R box providing email connected to Insight/Spectrum cable ISP 
I'm getting complaints of the following error:

> The original message was received at Wed, 20 Dec 2017 09:37:36 -0500
> from rrcs-96-11-138-58.central.biz.rr.com [96.11.xx.xx]
> 
>    ----- The following addresses had permanent fatal errors -----
> <xxxx at oxxx.xxx>
>     (reason: 550-5.7.1 [2607:fcc8:bbc1:af00:a6bf:1ff:xxxx:xxx] Our system has detected that)
> 
>    ----- Transcript of session follows -----
> ... while talking to aspmx.l.google.com.:
>>>> DATA
> <<< 550-5.7.1 [2607:fcc8:bbc1:af00:a6bf:1ff:xxxx:xxx] Our system has detected that
> <<< 550-5.7.1 this message does not meet IPv6 sending guidelines regarding PTR
> <<< 550-5.7.1 records and authentication. Please review
> <<< 550-5.7.1  https://support.google.com/mail/?p=IPv6AuthError for more information
> <<< 550 5.7.1 . s15si3306798ith.152 - gsmtp
> 554 5.0.0 Service unavailable

A quick Google shows this may be a problem for at least the last two years:

http://forums.businesshelp.comcast.com/t5/IPV6/Google-mail-requires-IPv6-PTR-record-but-Comcast-does-not-supply/td-p/27056

Is this fix, disabling IPV6 in postfix, applicable to 5209R?

http://tanguy.ortolo.eu/blog/article109/google-ipv6-smtp-restrictions

Hope I can get this fixed some users are migrating to outside personal 
accounts...


TIA! HoHoHo!