Since I had to look all over�for the correct settings and there was a
lot of trial and error involved (specially for the Realm). Thanks to Engin Support that finally provided this info after logging a support request.
The screenshots are from a Nokia E65, but should be applicable for similar Nokia phones.
Profile name: engin
Service profile: IETF
Default access point: {Your WLAN Access Point}
Public user name: sip:{phone number}@voice.mibroadband.com.au
User compression: No
Registration: When needed
Use security: No