You can add contacts from your organization's global address list (GAL), from a
federatedTwo or more organizations that are linked by using Lync Server, Office Communications Server, or Live Communications Server. After you add a federated contact to your Contact List, you can communicate with the contact by using any communication mode that is available in both organizations. network to Communicator for Mac 2011, or from the following networks: Windows Live, AOL, and Yahoo!. Windows Live
IDs include all e‑mail accounts ending in "@live.com," "@hotmail.com," "@msn.com," and other accounts that are registered with Windows Live.
You can also delete or block a contact from your contact list.
Do any of the following:
Add a contact from the global address list
Add a contact from Windows Live, AOL, Yahoo, or a federated network
Block a contact
Delete a contact
Block all unknown senders from sending messages