Keila
09/25/2026, 2:11 PMAI Evy
09/25/2026, 2:11 PMAI Evy
09/25/2026, 2:11 PMsip.retellai.com. This appears to be a call-specific investigation issue rather than something documented behavior.
What I can confirm from the sources: Retell's SIP server supports TCP, UDP, and TLS/SRTP transport, with TLS using the URI format sip:sip.retellai.com;transport=tls [(1) ]() [(2) ]() . Retell's SIP server presents a certificate signed by the Amazon Trust Services CA, and TLS handshake or certificate validation issues can occur particularly when an on-premises SBC or edge device is in the path, sometimes requiring the Root CA (and possibly the intermediate CA) to be installed in the trusted store of that device .
To debug this specific issue, I'd recommend capturing a PCAP of the TLS call and inspecting the SIP signaling flow directly. You can filter for sip traffic and look at the full call flow (INVITE → 200 OK → ACK → BYE) using Wireshark's Telephony → VoIP Calls → Flow Sequence feature [(3) ]() . Specifically check:
- Whether the BYE is actually sent by Retell but not reaching your endpoint (a TLS/firewall/NAT issue) , versus Retell not sending it at all
- SIP response codes and any errors in the signaling exchange
- That port 5061 (TLS) is open bidirectionally, in addition to your RTP media ports
Since this involves an active call-termination investigation, I'd suggest contacting support directly with the affected Call ID and a PCAP capture for deeper diagnosis:
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Would you like me to provide a general answer based on my knowlAI Evy
09/25/2026, 2:11 PMAI Evy
09/25/2026, 2:11 PMAI Evy
09/25/2026, 2:11 PMKeila
09/25/2026, 2:21 PMKeila
09/28/2026, 12:00 PMAI Evy
09/28/2026, 12:00 PMAI Evy
09/28/2026, 12:00 PMAI Evy
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09/28/2026, 12:00 PMAI Evy
09/29/2026, 11:26 AMKeila
09/29/2026, 11:26 AMAI Evy
09/29/2026, 11:26 AMAI Evy
09/29/2026, 11:26 AMAI Evy
09/29/2026, 11:26 AM