Hi, We have a Kamailio Instance running on Public IP Address, one of our ISP cannot send ACK back to us because we are sending 100 Trying - without "received" parameter. Is there any way in Kamailio to force a "received" parameter in the via header for 100 Trying Message? SIP/2.0 100 trying -- your call is important to us Via: SIP/2.0/UDP X.X.X.X:5060;branch=z9hG4bK8tgchsfjaKJdf.1;rport=5060 Thank you.