Security

I have a Linux Firewall on my Network that is setup with VPN. Every thing is working fine execpt Outlook.
When a client conects with VPN they can browse the entire Network, Map to Shares and transfer files ect...
The only think that is not workingis the conection with one of the three Exchange Server.
When a client attemptes to browes the Exchange Server, open Outlook or conect to a shared folder on the Exchange Server, they are told that the computer name or shared folder can not be found.
I CAN Ping that Exchange Server and I can see it in the Browse List.
I can conect to the other two Exchange Servers on my Network by name and do not have any other problems with the VPN or the Exchange Server.

Thanks For Your Time And Help