Assume that Domain Name System (DNS)-based automatic discovery is the only automatic discovery method that is deployed in a Microsoft Lync Server 2013 environment. In this situation, Lync 2013 clients do not discover the Exchange Web Service (EWS) servers.
To resolve this issue, install the following cumulative update:
2812461 Description of the Lync 2013 updates: February 2013
To work around this issue, use one of the following methods:
Deploy Http-based automatic discovery in the environment. Note The URL of the Http-based automatic discovery must be case sensitive.
Use a Lync 2010 client instead of a Lync 2013 client.