In an effort to provide enhanced capacity and service reliance, Windows Live Messenger will soon be adding additional IP addresses 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.
IP addresses that are used by MSN (Windows Live)
For more information please reference Microsoft KB 897567, or for further assistance, please engage Microsoft Customer Support Services via http://support.microsoft.com.