There are actually several ports you will need to open some for outbound and some for inbound. I suggest you open the outbound ( client ) only.
nat (inside) 1 access-list Inside_Out
global (outside) 1 interface
access-list Inside_Out permit tcp host any eq 5050
access-list Inside_Out permit tcp host any eq 80
access-list Inside_Out permit tcp host any eq 5100
access-list Inside_Out permit tcp host range 5000 5001
access-list Inside_Out permit udp host range 5000 5010
NOTE: if you have an access-list aplpied to teh inside interface then you need to modify that access list accordingly.
I hope it helps .. please rate it if it does !!!
Ports Yahoo! Messenger uses!
Yahoo! Messenger services uses a variety of ports.
Service Ports
Chat & Messenger TCP Port 5050: Client Access only
Insider/Room Lists TCP Port 80: Client Access only
File Transfer TCP Port 80: Server Access.
Your ISP may block this port, as its used for web hosting.
You can change port in Messenger, Preferences, File Transfer.
Voice Chat UDP 5000-5010
TCP 5000-5001: Client Access
If UDP Fails, TCP will be used instead, see below.
WebCam TCP Port 5100: Client Access
Super Webcam TCP Port 5100: Server Access
P2P Instant Messages TCP Port 5101: Server Access
PMs between Buddys may not use the Yahoo! Server, but this is not a requirement.