[OpenSER-Users] Add record route in reply route?

I have the following scenario: UA - OpenSER - SIPX - MicrosoftUM2007 As OpenSER has the public IP address and SIPX has no public IP, Openser has to be in the loop of all SIP messages. Therefore I set a record-route header in OpenSER. SipX is needed for the UDP/TCP gateway to MS UM2007 so therefore SipX needs to add another record-route header. UM2007 then receives a record with 2 record-routes (the one of OpenSER and the one of SipX) Unfortunately our UM2007 replaces the OpenSER record-route in the OK messages by the IP of SipX IP only, so Openser is out of the loop. The UA then tries to reply with ACK to the (private) IP of SipX and fails. My question: Ist here a chance to add another record-route with OpenSer's IP in OpenSER 1.3 in the reply route? According to the documentation in rr it doesn't work. Any hint is appreciated. Best regards Peter