Trying to get WCF to communicate cross-domains

Question

I'm trying to get two WCF services to communicate with each other in a cross-domain environment such that .NET web application calls service A on Server A in DMZ. Service A then calls Service B via SSL on Server B which is located in a secure Domain.

I'm currently able to get Service B up and running fine. I'm able to make calls to service B from within the Domain via SSL without any issues. However, once I try to make the call from service A or even simply the .NET web app I run into errors.

The errors I get change depending the endpoint and binding configuration I use. So far I've been using either wsHttpBinding or BasicHttpBinding...neither work for me.

Any suggestions or examples of what my endpoint and binding should look like?

Thanks

Dominic