### Answer Based on the current documentation, the official Retell SIP server URI is

sip:sip.retellai.com

[(1) ]() . This is the recommended URI for configuring origination (inbound calls) when setting up custom telephony with Retell AI . The URI you're using (

5t4n6j0wnrl.sip.livekit.cloud

) appears to be a LiveKit-specific endpoint that was referenced in one blog post example for setting up origination with Retell AI [(2) ]() . However, the official Custom Telephony documentation consistently references

sip:sip.retellai.com

as the Retell SIP server URI [(1) ]() . I don't have specific information in the available sources about whether the LiveKit endpoint will be deprecated. For the most current and reliable configuration, I recommend using the officially documented SIP server URI:

sip:sip.retellai.com

. If you need clarification on whether your specific endpoint will continue to be supported, you may want to reach out directly through Retell AI's support channels.

​ To learn more, see the sources I considered: [[1] Custom Telephony Overview](https://docs.retellai.com/deploy/custom-telephony) [[2] How to Choose the Right Telephony System in 2024 | Retell AI](https://www.retellai.com/blog/how-to-choose-the-right-telephony-system-in-2024) ​

Feel free to tag @AI Evy with additional questions. I also appreciate feedback, it helps me improve.