Reverse DNS lookup and Authoritative vs non-Authoritative responses
Posted on 2013-05-22
We have a frequent business partner that uses Cisco IronPort for email scanning/filtering. We use Zscaler for incoming and outgoing email delivery.
The Cisco IronPort product gives a high SBRS score if the sending server does not provide an Authoritative response to Reverse DNS lookup.
Zscaler says "There is nothing wrong with non-authoritative answers. You get authoritative answers if the responding DNS is responsible for that zone".
I use mstoolbox.com and never get an Authoritative response when I am checking Zscaler's servers.
I am looking for any information you can provide me with the differences with Authoritative vs non-Authoritative responses to DNS reverse lookup.
IsZscaler's response (in quotes above) correct?
Is it appropriate or common for an incoming email to receive a higher SPAM (SBRS) score because its sending server does not provide an Authoritative reverse DNS response?