Hello, we're trying to use Freeswitch as a Microsoft Teams direct routing SBC. So far everything works perfectly, except getting the call back from hold on an outbound call. The Problem is that Microsoft expects a Record-Route Header in every Request and every Response. I have been able to set/rewrite this Record-Route header with sip_h_ and sip_rh_ in most szenarios, but like i said - unhold on an outgoing call does not work. The hold is initiated with a reinvite with a=inactive in sdp, which does work. However, the unhold - also a reinvite with a=sendrecv in sdp does not work correctly. In the sip-trace i see that the OK ( in response to the INVITE for unhold ) gets retransmitted a couple of times, because the ACK from microsoft isn't received. This is due to the missing Record-Route Header in the OK Message. I have seen this behavior on inbound calls too, when i didnt set the Record-Route Header. Now my question: Is there any way to add the Record-Route Header to every Message on a sip-profile or gateway? Or if not, is it possible to handle a reinvite in dialplan so i could set the header manually? Maybe there is somebody who already has this working that could point me in the right direction. I know freeswitch isn't a SBC, but it would be nice to be able to use freeswitch as a Teams-SBC without Kamailio or something similar. Any help is very much appreciated 🙂 regards, Stefan