When you're integrating Microsoft Lync Server with Exchange Unified Messaging (UM), you have to run the ExchUcUtil.ps1 script in the Shell. The ExchUcUtil.ps1 script does the following:
* Creates a UM hunt group for each UM IP gateway. The pilot identifier of each hunt group specifies the UM SIP URI dial plan used by the Lync Server Front End pool or Standard
Edition server that's associated with the UM IP gateway.
* Grants Lync Server permission to read Active Directory UM container objects such as UM dial plans, auto attendants, UM IP gateways, and UM hunt groups.
* Creates a UM IP gateway for each Lync Server pool.
Reference: Configure UM to work with Lync Server
https://technet.microsoft.com/en-us/library/jj966276%28v=exchg.150%29.aspx