_sipinternaltls._tcp.contoso.com domain over port 5061 maps to sip.fabrikam.com
Note The Lync 2010 Phone Edition January 2013 cumulative update added the requirement of strict domain name matching for Lync 2010 Phone Edition devices automatic sign-in. The Lync 2013 Phone Edition devices enforce strict domain name matching.
_sipinternaltls._tcp.contoso.com domain over port 5061 maps to sip.contoso.com
Note Be sure that the Lync front end server pool certificate will have sip.contoso.com in its Subject Alternate Name (SAN) list.
DNS Requirements for Front End Pool
DNS Requirements for Automatic Client Sign-In
For detailed information on deploying certificates for Lync Server front end server pools, see the Microsoft TechNet documentation listed below:
Configure Certificates for Servers
The following Microsoft Knowledge Base (KB) article describes the Lync 2010 cumulative update for strict domain name matching:
Updates are available that add support for Lync Online in Lync Phone Edition
Article ID: 2933146 - Last Review: Feb 21, 2014 - Revision: 1