BYO SIP Trunk: Wrong FROM/To header in SIP REGISTE...
# supportj
Jens Prangenberg
03/09/2026, 12:03 PMHi Vapi Support Team,
I'm experiencing an issue with my BYO SIP Trunk integration where the SIP REGISTER request is sent with an incorrect FROM and To header.
My Credential ID: 87eaf4da-cd93-48a3-bd03-54557baa7a14
The SIP REGISTER is currently sent with:
From: ;tag=9ytacZU2H8cHB
To:
However, my SIP provider Placetel (Germany) requires the FROM and To header to be in this format:
From:
To:
I have configured the sipRegisterPlan as follows:
- domain: fpbx.de
- username: 777z9aywjl
- realm: fpbx.de
- publicIpInContactEnabled: false
Despite this configuration, Vapi ignores the domain and uses its own internal SIP domain (sip.vapi.ai) in the FROM/To headers instead of fpbx.de. This causes the registration to fail on Placetel's side.
Placetel support has confirmed that the REGISTER requests are reaching their system, but are rejected because the FROM header is incorrect.
Could you please fix the sipRegisterPlan so that the domain field is correctly used in the FROM and To headers of the SIP REGISTER request?
Thank you!
Jens Prangenberg
03/10/2026, 7:11 AMCan someone help me?
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Chiranjeet Mishra
03/12/2026, 5:29 AMHi,
Sorry for the inconvenience. We are currently investigating the issue and will share an update with you shortly.
Chiranjeet Mishra
03/12/2026, 8:21 AMHi,
I wasn’t able to locate the credential ID that was previously shared.
Could you please create the credential again and share the following details so we can investigate further:
1. The new credential ID.
2. The entire request and response from the SIP trunk creation process.
• Please make sure to redact the password or any sensitive credentials before sharing.
Once we have this information, we’ll review it and assist you further.
Thank you & have a lovely day!
Best regards,
Oshi Raghav
Customer Support Team | Vapi