You can greatly increase the benefits of your investment in Lync Server by enabling your users to communicate with external users. External users can include:

• Remote users   Your organization’s own users, when they are working outside your firewalls and are using their laptops or other Lync Server devices.

• Federated users   Users from companies you work with who also run Lync Server. To enable your users to easily contact these users, you create federated relationships with these companies.

• Public users   Users of public IM services, such as IM services provided by the Windows Live network of Internet services, Yahoo!, and AOL, and users of providers and servers that use Extensible Messaging and Presence Protocol (XMPP), such as Google Talk.

  Note:
  Note that a separate license might be required for public IM connectivity with Windows Live, AOL, and Yahoo!

  Important:

  As of September 1st, 2012, the Microsoft Lync Public IM Connectivity User Subscription License (“PIC USL”) is no longer available for purchase for new or renewing agreements. Customers with active licenses will be able to continue to federate with Yahoo! Messenger until the service shut down date. An end of life date of June 2014 for AOL and Yahoo! has been announced. For details, see Support for public instant messenger connectivity. The PIC USL is a per-user per-month subscription license that is required for Lync Server or Office Communications Server to federate with Yahoo! Messenger. Microsoft’s ability to provide this service has been contingent upon support from Yahoo!, the underlying agreement for which is winding down. More than ever, Lync is a powerful tool for connecting across organizations and with individuals around the world. Federation with Windows Live Messenger requires no additional user/device licenses beyond the Lync Standard CAL. Skype federation will be added to this list, enabling Lync users to reach hundreds of millions of people with IM and voice.

To enable any or all of these scenarios, you need to deploy an Edge Server to help enable secure communications between your Lync Server deployment and external users. Your organization’s remote users and users at federated organizations will be able to see each other’s presence and communicate using IM. For details about enabling communication with external users, see Planning for External User Access in the Planning documentation.

Lync Server provides features you can use if your organization must follow compliance regulations. You can use Archiving to archive the content of IM messages for all users in your organization or for only certain users that you specify. For details, see Planning for Archiving in the Planning documentation.

If you also have Microsoft Exchange Server 2013 deployed, you can integrate the archiving of Exchange data with the archiving of Lync Server data, and use a single tool to search both types of archived data. For more information, see Configuring Microsoft Lync Server 2013 to Use Microsoft Exchange Server 2013 Archiving.