My Outlook 2007 finally connects to Exchange 2003 with RPC over HTTPS proxy on Vista.

There is this application called "Windows Easy Transfer" that comes along
with Vista. Its in "All Programs" | "Accessories" | "System Tools" menu.
Among other things, it claims to be able to transfer email settings too. You
might want to give it a try.


Please try the following steps on the Vista client:

1. Click Start, click Run, type regedit in the Open box, and then click OK.
2. Locate and then click the following subkey:
   HKEY_CURRENT_USER\Software\Microsoft\Office\12.0\Outlook\RPC
3. On the Edit menu, point to New, and then click DWORD Value.
4. Type DefConnectOpts, and then press ENTER.
5. Right-click DefConnectOpts, and then click Modify.
6. In the Value data box, type 0, and then click OK.
7. Exit Registry Editor.
8. Please restart the client machine, re-configure the Outlook profile, and try again log on via RPC over HTTP

Again, my Vista setups did not have the RPC key on the computer. So, I created the key, created the value and rebooted the computer. Deleted the old outlook profile, created a new one and tested. This time it worked.