We have a Lync 2010 Standard with Enterprise voice system.  One server with everything collocated. SIP trunk is from Level3.  There is an Audiocodes M1kb SBC handling the traffic from the SIP trnaks to Lync.  We put in the referred-by as per the KB. Server ahs been rebooted twice and have tried the IP address of the LAN side of the SBC and also the FQDN which is what is in the Topology builder.

There is a 2nd GW in the topology builder as it handles some PBX traffic during migration, but no referred-by is required.

Reason the Referred-by is needed is for simultaneous ring and forwarding.  Both fail if a call that is NOT on the level3 system originates the call.  Calls that originate on their system work fine.

they told us the changes need to be made on our side.

details below:

Front End version is 4.0.7577.217

Mediation version is 4.0.7577.183

Mediation config file is:

<?xml version="1.0" encoding="utf-8"?>
<configuration>
  <appSettings>
                <add key="CLSIPSBC1.<company>.com.ReferredBySupported" value="true"/>
    </appSettings>
<runtime>
    <generatePublisherEvidence enabled="false"/>
  </runtime>
</configuration>

Hi,

Please install the latest update for Lync front end and mediation.

Please also contact your SIP provider to check if there is any invalid or conflict setting on their end.

Please also enable logging tool on Mediation Server for further troubleshooting.

http://blog.schertz.name/2011/06/using-the-lync-logging-tool/

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I also have the same issue in my lab.  With Refer Supported on the Trunk Configuration disabled and the latest CU9 installed on Lync,  when adding the same changes to the Media Config file as shown above, and saving the changes, restarting the entire server, it does NOT send a Referred-By header in a Invite my Gateway.  The call was originated by PSTN caller, answered by a Lync client and transfered to another PSTN number.  I never see the Referred-by header.  The Gateway and SBC I am using both support the Referred-By headers, so that is not the issue. when looking at the snooper trace, I never see the Referred-By header being added at the Mediation server when it is being created.  Looks to me like this file is never getting used. Any other possibility in the mediation server that would prevent this from getting used?