I have read the FAQ on getting Yahoo net2phone services to work via ISA. I tried setting up filter rules on ISA and testing the voice call feature with no luck. The connection wizard in Yahoo reports that TCP ports 5001 and UDP ports 5055 both need to be open. I confirmed this using Netmon on the client behind ISA, as was suggested in the FAQ. The packet filters were set up as "both" (bi-directional ?) and remote ports set to "all". No joy.
I tried to be clever and set up a corresponding canned "Net2Phone" protocol rule (hey it says powered by Net2Phone), but that did not help.

Yahoo online docs say, open the required ports and life is good. Howerver if ur behind a proxy, ur outa luck. What do they mean?

So what is the canned "Net2Phone" protocol rule that comes with ISA?

I really want to understand this.(sigh)

Hello,

Thank you for writing to Yahoo! Customer Care.

As of now, there's no way to do what you request. However, we may
include this feature in a future release. Your Yahoo! Messenger will
update automatically as soon as the new version is released.

Thank you for using Yahoo!, and please let us know if we can be of
further assistance.

Regards,

Customer Care

Original Message Follows:
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Subject: PCtoPhone-Problems and Questions

Operating System: Windows 2000

Web Browser: Microsoft IE 5.XX

Voice Error Message
Connection Test fails

Details:
Yes, I am behind a proxy
server/firewall. I opened up the ports
that the test dialog box says should be
opened (btw ur webpage differs on the
required ports), but no joy.
You guys point that if I use a proxy
server for internet access, then voice
chat won't work.
Can you suggest a proxy plugin, or some
sort of socks 4/5 thing to use with MS
Internet Security and Acclerator Server?