PTR recored Issue

Question

We have 2 Mail servers ( Internal and External) the External is hosted by ISPA with ip address of 62.xxx.xxx.xxx, we use to have the internet from the same ISPA, and the PTR record is already setup. We changed the ISP to ISPB with subnet of 154.xxx.xxx.xxx and the external mail is still in ISPA. Now we have issue sending emails and email are considered SPAM. My question is how is how will take care of the PRT record is it ISPA which still host the external mail or the new ISPB who provide the internet? Thnaks,

score 0 · Answer 1 · answered Jul 07 '20 at 14:28

It's the owner of the IP address that controls the reverse DNS records, i.e.

for the 62.x.y.z it's "ISP A"
for the 154.x.y.z it's "ISP B".

If you need send mail from both, you could e.g. name one mail-a.example.com and the other mail-b.example.com, but it's best you don't use the same name for both, as the receiving mail system may expect the name to be canonical and test that there are exactly one A record pointing to that exact IP.

Also remember to use the same names for your HELO hostnames & SMTP banners, respectively.

Recommended DNS configuration:

; On the authoritatice DNS servers of your domain
mail-a.example.com.          IN   A       192.0.2.10
mail-b.example.com.          IN   A       203.0.113.20

; ISP A
10.2.0.192.in-addr.arpa.     IN   PTR     mail-a.example.com.

; ISP B
20.113.0.203.in-addr.arpa.   IN   PTR     mail-b.example.com.

...vs. poor configuration (DO NOT USE THIS):

mail.example.com.            IN   A       192.0.2.10
mail.example.com.            IN   A       203.0.113.20
10.2.0.192.in-addr.arpa.     IN   PTR     mail.example.com.
20.113.0.203.in-addr.arpa.   IN   PTR     mail.example.com.

PTR recored Issue

1 Answers1