Exchange RPC-HTTP, Outlook unable to connect to exchange using HTTP

I have three computers that will not connect to a SBS 2003 Server using the HTTP Proxy. I have a valid SSL and tested it against OWA which works fine, no certificate errors. Because the three computers won't connect it apppears the problem is on the server and not with Outlook. Clients are using Outlook 2003 and 2007. Server is Exchange 2003 SP2

I notice in exchange I do not have the option to select RPC-HTTP front end server. Is this why clients can't connect Outlook to Exchange over the internet?
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Well assuming you have the port forwarding setup properly and RPC configured on the server, it should work fine. The 2 best articles on the internet on how to look for connectivity issues and how to set RPC up is below. Please carefully read the instructions without skimming through it.
Alan HardistyCo-OwnerCommented:
Please run the Outlook Anywhere (HTTP over RPC) test at and Specify Manual server settings.
Hopefully the results will be self explanatory, but if not, please come back for more help.
It may all be down to IIS permissions.

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