How can I make MSN Messenger work from behind a Firewall?

I have Zone Alarm Pro 4 installed on my PC. I use MSN Messenger and I can use Instant Messaging fine, but I can't make an audio conversation without shutting down Zone Alarm. (With Zone Alarm shut down MSN Messenger works fine. So Zone Alarm is definitely the villian.)

What do I need to enable on Zone Alarm to make Messenger work fully?
Roy Jones, October 2003


done
Messenger will work with Zone Alarm if you set "Internet Zone Security" on Zone Alarm to Medium. (Default is High.)

The difference between High and Medium is that the High setting makes your computer work in Stealth Mode. Your ports are protected and hidden from other computers. In Medium Mode your ports are protected in just the same way, but they are not hidden from other computers.

If you are concerned about lowering Zone Alarm's setting to Medium, you can set Zone Alarm to Medium while Messenger connects your Voice Conversation, and then put Zone Alarm's setting back to High as soon as you are connected.

Andy Lynch, October 2003
You can get an audio conversation working if you know the other parties IP Address.

Go to Zone Alarm..
1) Select Firewall
2) Select the Zones Tab
3) Click on the Add Button and select IP Address from the menu
4) Enter the IP Address (ensure Trusted is selected) enter a description, click OK.
5) Click on the word "Trusted" on the new entry in the Zones Table. Change this to Internet. You should now be able to connect for a voice chat, a file transfer, webcams etc...

Paul, October 2003