An email server in a residential setting will fail PTR unless you are
working with a medium sized/an ISP that cares about their customers.

see answer here

On 9 August 2017 at 23:34, Rupert Gallagher <> wrote:

> The dns still fails RFC1912 (ptr).
> Sent from ProtonMail Mobile
> On Wed, Aug 9, 2017 at 6:39 PM, Walter Alejandro Iglesias <
>> wrote:
> > Hello Rupert, In article you wrote: >
> Try the link again. The reason it showed false
> results was because IP was blocked in my pf firewall. I
> have a script to detect hacking attempts in my port 25 and block those IPs
> automatically. Thanks for your help anyways. And sorry if I didn't answer
> you before.>


Rui Ribeiro
Senior Linux Architect and Network Administrator

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