Hi everyone, I’m running into an issue with the Outbound Transport settings for a SIP-trunk connected number. For one number that’s working correctly, “Auto” is set as the Outbound Transport (I didn’t choose it manually – it just shows as “Auto”), and everything works fine. But for other numbers I’m trying to connect via SIP trunking, I only see TCP, UDP, and TLS as options – and none of them are working for outbound calls. Has anyone experienced this before? Is this a known issue, or could there be a bug on the platform? I’d really appreciate urgent help on this – I’m blocked from using outbound calls right now. Thanks in advance! https://cdn.discordapp.com/attachments/1458075375006519480/1458075375346384936/Bildschirmfoto_2026-01-06_um_13.30.39.png?ex=697958c3&is=69780743&hm=5e72962a7a46a92a102b5a84816188779c350f27acf42406ebefe7bf9cfb2eea&

Hello @L , what error you are seeing when you do outbound calls using this number and can you see the call in the call history on your provider ?

@Omar Ashraf | Community Lead Hi Omar, there’s actually no specific error message when I try outbound calls – they just don’t go through, and I don’t see anything in the call history on my provider’s side. What’s strange is: for one number, the Outbound Transport is automatically set to “Auto” – and with that, everything works perfectly. But for the other numbers I added later, I can only choose between TCP, UDP, and TLS, and none of them work. No traffic reaches the provider. If I could select “Auto” for the new numbers, I believe it would work too – but that option isn’t available. Could this be a bug or a config issue on your side? Thanks!

what is the sip URI you did use on your provider side?

@Omar Ashraf | Community Lead I didn’t have to set any SIP URI on my provider’s side – neither for the working number nor for the ones that don’t work. For outbound calls, we just use the SIP username and password. The SIP registrar can be seen in the first screenshot I sent.

Can you share your org id

@Omar Ashraf | Community Lead org_dd54NkGQRZgK2M37

which ones is working and not working

@Omar Ashraf | Community Lead - 917 is working, -916 not working, thanks for checking.

I see you get this error : Telephony_provider_permission_denied This means the sip trunk credentials are incorrect

@Omar Ashraf | Community Lead That can’t be the issue – I copied the data directly from the provider. I’ll quickly try it with a different number. It’s also possible that the provider (who I already contacted about this) is currently testing something with number 916. Please check number 911 – I just re-entered the login credentials there.

can you put the number in the E.164 format

sure, give me 4 min

ends with 902 your phone number right ?

this is my mobil number, yes

and you get nothing on your provider call history ?

yes, i get nothing. no i did not add this ips, so i should add this two ?

Yes, which is weird , The issue here that your provider is rejecting the call not the transport method..

i did add but still no change, can you see anything ? should i tell anything to provider - because i´m also in contact with them. https://cdn.discordapp.com/attachments/1458075375006519480/1458098838777630933/image.png?ex=695e67dd&is=695d165d&hm=12e1b777e0a90d0c0ad680b38201f519b45f0396fb10ac62889633b6ee43d043&

I’m also having a similar problem where mine can’t make outbound calls which is weird

@Omar Ashraf | Community Lead Hi, any update on this ?

Hello @L , I got with the team and your calls are rejected with 403 I will dm you the PCAP file You can reach out to their support and understand why they are rejecting your calls.

@Omar Ashraf | Community Lead could you pls check my private message to you. i did gave you there the feedback from our provider. thanks.

Responded.

@Omar Ashraf | Community Lead @User pls check my answer as well and give me a detailed feedback me and my provider do not understand you answer.

Okay.

@User @Omar Ashraf | Community Lead Hello Omar, can you please take another look at the messages above? I clearly mentioned that one number works and the other doesn’t. My provider confirmed that there is no technical difference between these two numbers. So how can the problem be with the provider? Please escalate this case to second-level support – we really need proper help here. My provider is ready to make changes, but they need a clear and logical explanation. And again: if one number works and the other one doesn’t, the problem is most likely not what you described above. Thanks in advance!

I did escalate and this was the team answer, and the issue here your provider is not allowing over 64 char in the sip which is very low most provider allowing over 256 char, you need to ask your provider to remove this limitation , why the other one were working because it was set to AUTO , which was removed.

@Omar Ashraf | Community Lead @User pls check: wenn retell.ai die Länge des From-Headers nicht anpassen kann, liegt hier eine Inkompatibilität bei ausgehenden Anrufen mit easybell vor. Unsere Voice-IT wird die zulässige Header-Länge nicht für einen einzelnen Anbieter erhöhen, da das bestehende Limit für tausende andere Kunden und Telefonsysteme ausreichend ist und dahingehend keine Probleme bekannt sind. Es würde schon reichen 'transport=tcp' aus der From-URI zu entfernen. Für unsere Systeme ist dieser Zusatz nicht erforderlich. Der Transportmechanismus wird ausschließlich über den Via-Header und den tatsächlich verwendeten Transport bestimmt.