We have an exchange 2003 server set up that works fine if an Outlook 2003
client accessing using RPC over HTTPS with basic authentication running on xp
sp2

With Outlook 2007 clients on XPsp2, the client will connect to the server
inside the office but will not connect from outside. I can, however download
the certificate and resolve the server name and user ID using HTTPS from
outside. On the 2007 install, both the check boxed for http first then tcpip
are checked and the security is set to Kerberos/NTLM security (I have tried
all combinations)

Starting outlook 2007 from outside the LAN using /rpcdiag just shows that
outlook is trying to connect, fails and then retries ad infinitum.

Connecting to OWA works fine and connecting to
https://mail.servername.com/RPC/rpcproxy.dll will give me the blank page with
the padlock as it should, leading me to believe that the HTTPs is fine and
the problem lies somewhere in Outlook. The same issue is happening on 2
separate PCs

Any suggestions?