Turn the destination back to any
Enable logging for the policy
Create a number of successful skpe calls
Go to the policy > log page
Download the logs and analyze the destination addresses needed for the successful calls
Duplicate the policy so there are two in a row exactly the same
Update the FIRST policy to have only these destinations found in the logs
Continue to allow calls to be made
Now analyze the log for the second policy only
Add more destinations as needed to policy one
When you no longer have hits on the second policy disable/delete the policy as your have all you need now in policy one