Can't register at SIP server

[kanaille11]

Hallo,

I can't get my T46G running with my phone provider's SIP server. I configured the account and server settings correctly, but registration at the SIP server always fails.

To see what's wrong I analyzed and compared the SIP packages of the T46G with the SIP packages of another IP phone where registration works:

Other phone:
1. Sends SIP REGISTER request
2. Server answers with status 401, Unauthorized. There is a WWW-Authenticate header with a Nonce in this response.
3. Phone sends another SIP REGISTER request, with an Authorization header that contains the Nonce.
=> Registration successful.

T46G:
1. Sends SIP REGISTER request. All fields are the same as on the other phone.
2. Server answers with status 401, Unauthorized. There is a WWW-Authenticate header with a Nonce in this response.
=> Registration not successful. Retry with 1.

How can I configure the T46G to send a SIP REGISTER with an authorization-header?