This example is assuming you are in your office and connecting your Nokia E51/E66 to the network via a wireless LAN, the SIP extension is 1234 and the IP address of the Siemens Hi-Path OpenOffice is 192.168.1.222 so you’ll have to change those, but the rest should be fine. This process should also work for other telephone systems with SIP capabilities.
Go to Tools > Settings > Connection > SIP Settings
If a profile exist, you can edit it, if not create a new one.
Profile Name: Whatever you like, but I would recommend you enter the extension number
Service profile: IETF
Default access point: Set your wi-fi
Public user name: 1234@192.168.1.222 (will display as sip:1234@192.168.1.222 when saved)
Use compression: No
Registration: Can be either when needed or always on, but if you want to receive calls I’d say always on, but will reduce battery life.
Use security: No
Proxy Server Settings
Proxy server address: 192.168.1.222 (will display as sip:192.168.1.222 when saved)
Realm: 1234
Username: 1234
Password: enter your password
Allow loose routing: Yes
Transport type: Auto
Port: 5060
Registrar server
Registrar server address: 192.168.1.222 (will display as sip:192.168.1.222 when saved)
Realm: 1234@192.168.1.222
Username: 1234@192.168.1.222
Password: enter your password
Transport type: Auto
Port: 5060
Then go to Tools > Settings > Connection > Internet tel.
Create a new profile
Name: 1234
SIP profiles: select the SIP profile you created by using the above