Yeastar S-Series - Telekom CompanyFlex SIP-Trunk Configuration example


1. There is now a Template available Called CompanyFlex

2. If you Have trouble to make Outging calls. Why recently can't make outgoing calls through Companyflex sip trunk? – Yeastar Support

Because i had some trouble to get my Yeastar S50 running with my new Telekom Company Flex SIP-Trunk i thought i share some details.

It is quite similar to this post so read it maybe first. Recommended SIP Configuration for Deutsche Telekom – Yeastar Support

One thing to note is that this configuration will only work when the internet connection is done via the associated Telekom DSL Line. If you want to use an CompanyFlex Sip-Trunk with an internet connection from a different ISP you need to use TLS, SRTP, SAVP and MediaSec. But i could not get that working. (I don’t think it is supported).

Please also keep in mind that you use a appropriate DNS server. Preferably one from the ISP.
Google ( / and  Quad9 ( should work but is UNTESTED from my site.

The first step after making sure you have proper network settings is that you activate TCP with port 5060 in the General>SIP>General tap

Then you need your SIP trunk information at hand. I got mine from BSP Service portal (bsp.t-mobile.de).

Here is an Example how they can look like.

You create a new Blank SIP Trunk and select as Transport TCP and enable Outbound Proxy.

You fill

  • The value from “SIP-Domain” into “Domain”
  • The value from “Outbound-Proxy” into “Hostname/IP” and “Outbound Proxy Server”
  • The value from “Registrierungsrufnummer” into “Username” and “Caller ID Name”
  • The value from “Telefonie-Benutzername” into “Authentication Name”
  • In the Field "Caller ID Number" I did put the Trunks SIP number in the Format +(Country Code)(Area Code)(Number) without Extension number like +4969123456
  • In the Field "Password" obviously inserted the password from "Telefonie-Passwort"

The Port 0 works fine for me.

I did config my Advanced tap like that.

Telekom Supports G.711A (a-law),G.722, G.711U(u-law), G.729 as Codecs.

Because i selected in P Asserted Identity “DOD Number” i need to add DOD Numbers in the DOD tab. If you don’t do this, External Calls will be made with the Number in the “Caller ID Number” field from the Basic tab.

The DOD number is in my Case +(Country Code)(Area Code)(Number)(Extension) - Example +496912345610, +496912345611, +496912345612, +496912345613 …

Please don’t forget in and outbound Routes.

For Inbound it is +(Country Code)(Area Code)(Number)(Extension)

For Outbound

This will create the typical (in Germany) leading Zero for outgoing calls.



Please be aware that there a maybe other (and better) ways to achieve this but i hadn't any problems with it.

Also a shout out the the Yeastar support for their help!


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