Sorry for the late responses guys.
What exact features were you looking for with the messenger app? I used to use MSN Messenger all the time when I was running windows, and aMSN has all the features I used. I'm not sure how heavy of an MSN messenger you are, but it does the nudges and it does the smiles, video does work on it.
I was referring to actual port on your router. You would have to look up how to do this for your particular router. For linksys routers you would go to 192.168.1.1 and login and then proceed to porforwarding, it would be under gaming and applications I believe. On aMSN go to preferences and then connections. Under file transfer, peer to peer and nat settings, there's a port option, make sure that port is open by portforwarding it to a port you opened.
Before I opened that port for aMSN all the recipient would see is a black screen.
Hope that helps, let me know if you have any other questions, and I'll help you out if I can.