On May 22, 2008, Yahoo! Inc. will move their servers that provide instant messaging (IM) federation with Microsoft Office Communications Server 2007 and with Microsoft Office Live Communications Server 2005. These changes may affect users of these products.

This change will affect only those users whose external firewalls accept traffic on TCP port 5061 only from known IP addresses. If your external firewall accepts incoming TCP traffic on port 5061 from any IP address, this change will not affect you.

Yahoo! will not change the name of the service provider for instant messaging. This name will remain lcsap.msg.yahoo.com.

If your external firewall accepts traffic on TCP port 5061 only from known IP addresses, make sure that the following fully qualified domain names (FQDNs) and IP addresses are among the known addresses:

•	ap-ext1.lcs.msg.vip.sp1.yahoo.com
•	ap-ext1.lcs.msg.vip.ac4.yahoo.com
•	ap101.lcs.msg.ac4.yahoo.com 76.13.22.8
•	ap102.lcs.msg.ac4.yahoo.com 76.13.22.9
•	ap103.lcs.msg.ac4.yahoo.com 76.13.22.10
•	ap104.lcs.msg.ac4.yahoo.com 76.13.22.11
•	ap101.lcs.msg.sp1.yahoo.com 98.136.47.8
•	ap102.lcs.msg.sp1.yahoo.com 98.136.47.9
•	ap103.lcs.msg.sp1.yahoo.com 98.136.47.10
•	ap104.lcs.msg.sp1.yahoo.com 98.136.47.11

Note How you configure your firewalls depends largely on the firewalls that you use in your organization. Follow the manufacturer's instructions for configuring each firewall.

Make sure that the server configuration of Office Communications Server and of Live Communications Server Access Edge matches the recommended configuration settings. These settings are documented in the following deployment guides: