Hello, @User I'm setting up Zadarma BYO SIP trunk with Vapi for outbound calls but getting 407 proxy-authentication-required error. Inbound works fine. Has anyone successfully configured Zadarma outbound calling with Vapi? Any tips would be helpful. https://cdn.discordapp.com/attachments/1482178545311547575/1482178545672388791/image.png?ex=69b601d6&is=69b4b056&hm=cf034617b711decc24662fb9e21d493ce89d2231445997fc4e3f7fd14242ced2&

To resolve the 407 Proxy Authentication Error for outbound calls with Zadarma, ensure your SIP trunk credential in Vapi includes the correct

outboundAuthenticationPlan

with your Zadarma SIP number and password. Here’s the required configuration:

json
{
  "provider": "byo-sip-trunk",
  "name": "Zadarma Trunk",
  "gateways": [{ "ip": "sip.zadarma.com", "inboundEnabled": false }],
  "outboundLeadingPlusEnabled": true,
  "outboundAuthenticationPlan": {
    "authUsername": "YOUR_SIP_NUMBER",
    "authPassword": "YOUR_SIP_PASSWORD"
  }
}

Replace

YOUR_SIP_NUMBER

and

YOUR_SIP_PASSWORD

with your actual Zadarma credentials and update your Vapi credential accordingly. This should resolve the outbound authentication error according to the documentation I have found. Source: - [Vapi SIP Trunk Documentation](https://docs.vapi.ai/advanced/sip/sip-trunk)

407 usually means the SIP proxy isn’t getting the right authentication for the outbound request. With Zadarma + Vapi this often happens if the SIP auth ID, password, or proxy domain isn’t set correctly in the trunk. Inbound working is a good sign the connection is fine. Are you using your Zadarma SIP credentials or a PBX extension for the outbound auth? @Mehedi

hi, could you please provide the credential id or phone number that the SIP trunk is attached to? you can either send it to support@vapi.ai or DM me directly if you prefer to not share here.