Federated users are users who possess valid credentials from a federated partner, which is a trusted outside organization that is enabled for access to your Office Communications Server 2007 R2 deployment. To enable federated users to participate in group chat, you must create a federated user group to hold these users. All federated user groups are automatically added to the root scope when they are created. For details about how to segment the category hierarchy before you enable federated user access, see Understanding Scope and Membership.
To add a federated user group to the scope of the root category
On the Filemenu, click Manage Users.
On the Filemenu, click Create a New Federated User Group.
Type a name for the new group, and then click OK.