In an effort to provide enhanced capacity and service reliance, Windows Live Messenger will soon be adding an additional IP address used for PIC/Federation traffic. Some organizations have chosen to restrict this type of traffic to specific IP addresses, as referenced in Microsoft KB 897567 (http://support.microsoft.com/kb/897567). With this in mind we want to give you advanced notice of our intended change if you have configured your enterprise network in this manner.
Please ensure your enterprise firewall configuration is updated with the full list of Windows Live Messenger addresses below on or before Friday, February 2, 2010. Windows Live Messenger will NOT enable the additional IP addresses until on or after February 2, 2010 (Pacific Time) to ensure your services will not be disrupted by this change.
IP address for Windows Live Messenger PIC/Federation:
126.96.36.199 (Additional new IP address)
For more information please reference Microsoft KB 897567, or for further assistance, please engage Microsoft Customer Support Services via http://support.microsoft.com.