Hi Guys
Thanks for all your recommendations.
I did the change and rr headers only show the fqdn of Kamailio as you can see below in the 200 OK sent back to MS Teams, however still the same issue no ACK.
|||||||||||||||||||| ==================== tag: snd pid: 31232 process: 6 time: 1613047849.768857 date: Thu Feb 11 14:50:49 2021 proto: tls ipv4 srcip: 82.102.42.58 srcport: 5061 dstip: 52.114.132.46 dstport: 5061 ~~~~~~~~~~~~~~~~~~~~ SIP/2.0 200 OK Via: SIP/2.0/TLS 52.114.132.46:5061;branch=z9hG4bK4f5c9b66 Record-Route: sip:sbc.intelligentsupport.eu:5060 ;ftag=dcea3c9546914ff8826afca13260da1c;lr=on Record-Route: sip:sbc.intelligentsupport.eu:5061 ;transport=tls;ftag=dcea3c9546914ff8826afca13260da1c;lr=on Record-Route: sip:sip-du-a-us.pstnhub.microsoft.com:5061;transport=tls;lr From: Phillip Kyriacousip:+35722010058@sip.pstnhub.microsoft.com:5061 ;user=phone;tag=dcea3c9546914ff8826afca13260da1c To: sip:+35796552237@sbc.intelligentsupport.eu:5061 ;user=phone;tag=as63d965d3 Call-ID: 43f0f0be2fa05b408c81736dbe392aef CSeq: 1 INVITE Server: MediaGW V1.0 Allow: INVITE, ACK, CANCEL, OPTIONS, BYE, REFER, SUBSCRIBE, NOTIFY, INFO, PUBLISH, MESSAGE Supported: replaces, timer Session-Expires: 1800;refresher=uas Contact: sip:+35796552237@82.102.42.52:5060 Content-Type: application/sdp Require: timer Content-Length: 339
v=0 o=root 601931926 601931926 IN IP4 82.102.42.52 s=ASTERISK c=IN IP4 82.102.42.52 t=0 0 m=audio 16360 RTP/SAVP 0 8 101 a=crypto:1 AES_CM_128_HMAC_SHA1_80 inline:IyrJsjVV0w5ORJQ3OJB0r8iyRZU+1lMjg4i9vzC2 a=rtpmap:0 PCMU/8000 a=rtpmap:8 PCMA/8000 a=rtpmap:101 telephone-event/8000 a=fmtp:101 0-16 a=maxptime:150 a=sendrecv |||||||||||||||||||| ====================