What is the correct reverse DNS for a reseller using a private shared IP?

[WebHostPro]

A reseller account normally uses the server hostname for the PTR reverse dns but when the reseller uses a shared dedicated IP for the reseller main account and the accounts under it. What is the correct reverse DNS for that dedicated shared IP?

I have tried to point it to the server hostname and the main reseller account domain but both have an error in cPanel.

To fix this problem, contact your system administrator and request that they replace all PTR records for “123.123.123.1” with the following record at “ns1.webhost.tld” and “ns2.webhost.tld”:

Suggested “PTR” (PTR) Record PTR
Name

 

[cPanelMichael]

Hello @WebHostPro,

Can you browse to the Domains and IPs tab in WHM >> Exim Configuration Manager >> Basic Editor and confirm how the following options are configured?

Send mail from the account’s IP address
Reference /etc/mailhelo for custom outgoing SMTP HELO
Reference /etc/mailips for custom IP on outgoing SMTP connections

Additionally, can you confirm if this server uses a 1:1 NAT setup?

Thank you.