For many years I have been running ISA 2000 on a windows 2000 server. This ISA server is configured for VPN access (PPTP). There have been no issues access network services - in particular MAPI connection from Outlook to internal Exchange server.
So recently I setup a new server running windows 2008 R2 and TMG 2010 SP2 - configured for VPN access just like my ISA 2000 server.
Everything I have tested to date runs the same EXCEPT the outlook MAPI connections. On the TMG 2010 outlook can connect to the Email server and perform all functions, but it is very slow.
I ran some tests using rpcping and the ISA 2000 VPN is about 200ms whereas the TMG 2010 vpn is about 5,400ms.
Both ISA servers are domain members and are configured the same. The only difference is one is ISA 2000 on windows 2000 and the other is TMG 2010 on WIndows 2008 R2.
I have researched this for a very long time and have tries many experiments to try to determine why the TMG 2010 has such slow RPC response. I see a lot of posts for RPC over HTTP, but hardly any relating to RPC through a vpn tunnel.
I would appreciate the input of anyone who has also encountered this issue.