Mailing List CGatePro@mail.stalker.com Message #104171
From: Tom Rymes <trymes@rymes.com>
Subject: Re: Blacklist by DNS name [(host name is unknown)]
Date: Thu, 02 May 2013 13:58:31 -0400
To: CommuniGate Pro Discussions <CGatePro@mail.stalker.com>
On 05/02/2013 1:31 PM, Mark J Strawcutter wrote:
On 5/2/2013 1:28 PM, Juergen P. [core] wrote:
On Thu, 02 May 2013 11:55:43 -0400
  Mark J Strawcutter <mjstraw@iup.edu> wrote:
"also mx without working ptr records can be blocked"

You never receive connections from MX hosts so there's nothing to
block.

right, MX records themselves are not used when sending outbound mail.
However, some mail servers setups require that the domain of the from
address have the necessary DNS records to support incoming mail, in
which case you need either an MX or A record on that domain (prevention
of misdirected bounces and backscatterers only to mention a few cases of
mail exchanger abuse.. ) therefor the wohle setup-scenario is part of
the game ..
>
> and PTR records aren't part of that...
>
> Mark

Regardless of the outcome of this "theory vs. practice" debate, I really wonder how beneficial checking a PTR is going to be. AFAIK, most ISPs define generic PTR records for their IP Addresses, so most hosts will have some PTR record or another, even if it is meaningless.

Like this:

>nslookup 70.90.102.90
Server:  mercury.rymes.internal
Address:  192.168.0.254

Name:    70-90-102-89-ma-ne.hfc.comcastbusiness.net
Address:  70.90.102.90

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