Any help how to set up Reverse DNS?

For the typical CentOS Web Panel user, (using Freedns.org for DNS), and assuming we have a cooperative Internet provider willing to oblige (to give us reverse DNS for only one IP address), how do we set up Reverse DNS so our e-mails arrive at their destinations?

Thanks,

Matthew

openvz, KVM or any ?
basically you need to contact the host provider / vps provider