Symptoms
When you try to send an SIP Transfer (REFER) request to a federated endpoint, the transfer fails and returns a "403 Forbidden" error message in Microsoft Skype for Business Server 2019.
On the remote federated side, the REFER request is rejected by the Edge server, and you receive the following error message:
ms-diagnostics: 1019;reason="Referred-By header parameters are not valid";ErrorType="The referrer authentication parameters are not recognized";Referrer="<referrer_email_address>";HRESULT="0xC3E93C52(SIPPROXY_E_REFERRER_IDENTITY_INVALID)";source="sipfed.comput
Resolution
To fix this issue, install the December 2021 cumulative update 6 for Skype for Business Server 2019, Core Components.
