I think you will have to install ISA in integrated mode. Then try these settings. I have used them its working You need to create the following protocols definitons (under Policy Elements): 1. Yahoo! Voice #1 TCP Port 5001 Outbound 2. Yahoo! Voice #2 TCP Port 5000 Outbound 3. Yahoo! Voice UDP UDP Port 5000 Receive Send 4. Yahoo! WebCam TCP Port 5100 Outbound Of course, after you create these you need to add a protocol rule for them under Access Policy, or, add them to an existing rule. Unless you have an allow all rule, then no changes needed.