OK I have been trying to get RPC over http to work for past 3 days but no use. I have searched and searched the internet tried many thing but nothing seems to help. Here is my situation. I have 2 domain controller (DC1 and DC2) DC 1 is also exchange front end server and OWA is running on it (FORM based authentication) I configured DC1 to be the RPC proxy server. I also have 2 addational exchang Back end servers (EX1 and EX2) configured both the servers as Exchange back end RPC over HTTP servers. I am using watchguard firewall both prot 80 and port 443 are natting to DC1 for OWA access. My internal active directory domain is xxx.local and external domain is yyy.com OWA works fine internally and externally. OWA is accessible from external network at mail.yyy.com I was trying to test it with a mailbox on EX1 so I have made the following registry changes to both DC1 and EX1 [HKEY_LOCAL_MACHINE\SOFTWARE\Microsoft\Rpc\RpcProxy] "ValidPorts"="DC1:100-5000; EX1:6001-6002; EX1.xxx.local:6001-6002; DC1:6001-6002; DC1.xxx.local:6001-6002; mail.yyy.com:6001-6002; EX1:6004; EX1.xxx.local; DC1:6004; DC1.xxx.local:6004; mail.yyy.com:6004; EX1:593; EX1.yyy.local:593; DC1:593; DC1.xxx.local:593; mail.yyy.com:593;" What am I dong wrong. Any Help in this matter would be appriciated.

Hi guys. still working on this issue. Please help