Error connecting email security gateway please check network and configuration settings"

please note our  current scenario,

1. Websense C interface is on private ip subnet and Nat to public ip for internet access
2. E1 interface is configured with  public ip address
3. On the server there is NIC bonding on a private subnet ip

when we install triton email security gateway ,it asks for C interface ip address when we gave  C interface private ip and click Next it says "Error connecting email security gateway please check network and configuration settings"

Now please tell us the smooth resolution we are getting late secondly the scenario is mentioned above is correct ?  or we should bring E1  to same private ip subnet  as for C interface and log server interface.if any interface required internet we will Nat on internet.

Urgent Response is required