Set up LDAP Passthrough

HI,

All I can find is how to set up the Router to connected to internal LDAP server, this I have working but I want my external email filtering service to connect.

I thought I had it set but im more of a Cisco guy. Can anyone help me? I have what I thin is a both way IPv4 Poliicy set and a virtual IP set for the port forwarding but now joy.

Thanks