PFSense with CPanel and WHMCS

I have a server with a Pfsense firewall and a CentOS 7.0 Server running Cpanel and WHMCS.

Here is the IP Schema:

Firewall Public IP: x.x.x.202

Firewall Private IP: 192.168.2.1

Server IP: 192.168.2.9

I have PFsense configured with NAT to ports 80,443,25,110, (2086, 2087, 2093) (Wan to Lan IP 192.168.2.9) required by Cpanel

All functions of the CPanel work Great and I am able to communicate using the Web browser. But when I use a server connect fromWHMCS to CPanel using the external Public IP I get a message that it cannot communicate with Cpanel using 2087 (default communication port). I can however use the private IP: 192.168.2.9 on the WHMCS Module to communicate and everything works just fine, butthe WHMCS folks do not recommend that at all. Hence the conclusion is that some PFSense is blocking port 2087 from communicating both ways,...