Here is a list of the ports MSN Live uses:

• Messenger server: port 1493, 1542, 1863, 1963, 80 TCP and 443 TCP
• File Transfer/Sharing Folders: local: 1544 and 6891 – in fact 6720-65535 TCP from one source
• Messenger Update: remote: 80 local: 1457
• Remote Assistance If available): 3389 TCP
• Audio: local: , 1556, 11771, 13803 and generally 5004-65535 UDP
• Remote Desktop and whiteboard: local/remote: 389, 522, 1503, 1720, and 1731
• Launching Games: 80
• Video Conference: TCP 9000-9999, 5004-65535 UDP + 80
• Sign-In: remote: 443 local: 1484, 2400