Win7 Outlook RPC-HTTP SBS 2003

Hi I have an SBS 2003 server with a self certified certificate, several clients running XP with Outlook 2003 which connect using RPC-HTTP with no problem.

I have a new Win7 64bit client (I’ve installed the server certificate and I don’t get certificate errors if I connect to the https:\\server\remote page) that will not connect from Outlook. It does work when on the internal network (using RPC-HTTP), just not from the Internet…

Any ideas greatfully received…