[Ekiga-list] Configuration Ekiga 3.2.7 (Windows) for 1&1 SIP account

[c monty web de]

 Hello!

I'm failing to configure the SIP account correctly.
I enter the following data:
Name: <anyname>
Registrar: sip.1und1.de
User: <1und1 phone number starting with 49...>
Authentication User: <1und1 phone number starting with 49...>
Password: <password>
Timeout: 3600

Using another application "PhonerLite" with exactly the same data, the connection works.

But with Ekiga 3.2.7 I get this error message:
Status: Cound not register (Forbidden)

Are there any other configuration settings that needs to be modified?

THX