Hi Retell Support Team,
I’m integrating Retell AI with my Telnyx phone number +1 669 310 xxxx via TeXML webhook, and all Telnyx side configurations have been fully set up correctly:
My US number is bound to a TeXML application named RetellAI-Inbound on Telnyx.
Inbound calls from my Chinese mobile can successfully reach Telnyx servers and trigger your webhook URL.
Telnyx routing, POST method and TeXML settings are all configured following official guides.
Current Issue
Every inbound call triggers a voice error message: “We are sorry. An application error has occurred. Goodbye!”, then the call gets disconnected immediately.
Telnyx’s call debugging logs confirm the error response comes entirely from Retell AI’s endpoint, not Telnyx.
My Webhook Info
The URL I filled in Telnyx TeXML App:
Telnyx technical feedback points out this URL is incomplete — it requires my unique Agent ID appended at the end, formatted as https://api.retellai.com/texml/v2/YOUR_AGENT_ID.
Requests for your support
Confirm my correct full TeXML inbound webhook link with my agent ID included.
Check if there are any misconfigurations, API key failures or credit/subscription issues on my Retell agent account causing this application error.
Guide me through any missing agent publish/activation steps to fix the inbound call failure.
Looking forward to your quick reply to resolve this calling error.
Hey @1403320771 thanks for the detailed write-up. The issue isn’t your agent ID or account status: Retell doesn’t expose a TeXML webhook endpoint at all. https://api.retellai.com/texml/v2 is not a real Retell URL, and there is no /texml/v2/{agent_id} variant either. Telnyx is playing its own generic “application error” message because it isn’t receiving valid TeXML back from us.
The supported way to connect a Telnyx number to Retell is Elastic SIP Trunking, not a TeXML Application. Full walkthrough: Telnyx - Retell AI
High-level steps:
In Telnyx: detach +1 669 310 xxxx from the TeXML Application, then create an Elastic SIP Trunk (type FQDN). Add FQDN sip.retellai.com as an SRV record, transport TCP, E.164 number format, codecs G722/G711U/G711A. Set up outbound credentials (username + password) on the trunk and assign the DID to it.
In Retell: Phone Numbers → import the DID (or POST /import-phone-number), using the Telnyx FQDN (e.g. sip.telnyx.com) as the Termination SIP URI, the trunk’s username/password, and the X-Telnyx-Username: <username> custom SIP header.
Bind an Inbound Call Agent to the imported number in the Retell dashboard so calls have an agent to answer.
Once the number is on the Elastic SIP Trunk pointed at sip.retellai.com and imported with an inbound agent bound, inbound calls should connect.