Changes to Yahoo IM federation may affect users of Office Communications Server 2007 and Live Communications Server 2005

Thankfully, this has nothing to do with the buyout talks.

On May 5, 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.

You can read more about it, and the IP changes, here.