We have a customer with a dedicated IP address (say 10.0.0.1 and domain is example.com) - The customer has reverse DNS record setup to point 10.0.0.1 - example.com. We want the customer to use their own IP to send mail. We're getting the following errors on mxtoolbox: Reverse DNS is not a valid Hostname Reverse DNS does not match SMTP Banner This, from my understanding, is because the Reverse DNS is pointing to their domain name and not a valid hostname. In this case our hostname would be the same as the cpanel server (example cpanel.host.com) so although the reverse DNS record will resolve to their domain, it will never show to expected hostname as these 2 are different. We have not experienced any real issues even with the warnings from mxtoolbox, but from a customer standpoint we would rather want to give an all clear and change the setup on our end where needed. How would one change this above to work correctly? The reverse dns would never be able to be both the customers domain name (which I suspect is the issue here) as well as "the" valid hostname. I suspect a workaround here is to have a custom hostname to appear during the mailhelo but I'm not sure if it will work the way it should and if this is best practice. We could change the reversedns records to say something like example.host.com but that again would not resolve correctly. Any advice on this above?