It’s no problem to have Apache listening on a private IP address because the PIX or ASA handles the public to private IP address translation.  But for DNS, when a zone is queried, it can’t provide a private IP address and expect an outside server to be able to resolve it.  That’s where the fixup, static, and alias commands come in handy.

There are a few IOS rules that will help out immensely with cPanel and DNS translation.

Cisco to the rescue! This will enable the firewall to provide address translation to DNS packets:
fixup protocol dns maximum-length 512

A static NAT mapping must exist, associating the public & private IP:
static (inside,outside) cpanelserver.ext cpanelserver.int 255.255.255.255

An alias must be created which allows translation inside the private network:
alias (inside) cpanelserver.int cpanelserver.ext 255.255.255.255