PROBLEM DESCRIPTION: I encountered an issue where blind transfers fail from Polycom VVX phones when the original caller and the intended transfer destination are both external PSTN numbers. The transfer fails with the following error messages:
SIP/2.0 404 Not Found
ms-diagnostics: 10404;source="<LYNC FE MED POOL FQDN>";reason="Gateway responded with 404 Not Found (User Not Found)";component="MediationServer";SipResponseCode="404";SipResponseText="Not Found";sip-reason="Q.850;cause=3;text="No Route to Destination"";GatewayFqdn="10.1.20.3;trunk=10.1.20.3"
ms-diagnostics-public: 10404;reason="Gateway responded with 404 Not Found (User Not Found)";component="MediationServer";SipResponseCode="404";SipResponseText="Not Found";sip-reason="Q.850;cause=3;text="No Route to Destination""
Reason: Q.850;cause=3;text="No Route to Destination"
ms-trunking-peer: 10.1.20.3;trunk=10.1.20.3;User-Agent="SONUS SBC1000 4.1.1v377 Sonus SBC"
ms-endpoint-location-data: NetworkScope;ms-media-location-type=intranet
ms-application-via: ms-udc.cdr%3D9454b4d60a8874d7c7acb845a0a77d78%3A5;ms-pool=LYNCPOOLdomain.com;ms-application=http%3A%2F%2Fwww.microsoft.com%2FLCS%2FUdcAgent;ms-server=<LYNC FE MED POOL FQDN>
CAUSE: In the Sonus SBC settings under Transformation section, there were explicit transformation entries to match on internal User DID's for the Calling Address/Number.
RESOUTION: Needed to add a catch all transformation entry that matched on any Calling Address/Number since explicit matchings exist (see screenshot below).
