Polycom RMX 1500 Administrator's Manual page 1105

3
Click the SIP Servers tab.
4
Make sure that the SIP Server is set to Specify.
5 Make sure that the SIP Server Type is set to Microsoft.
6
Make sure that the IP address of the Office Communications Server
2007 or Lync Server 2010 is specified and the Server Domain Name is
the same as defined in the OCS/Lync Server and in the Management
Network for the DNS.
Polycom RMX 1500/2000/4000 Administrator's Guide
H-119