As a prerequisite you should have already registered an account with justvoip.com or another BETAMAX service of your choice.

First you have to get the current Version of the VoIP Settings (V.3.0 at the time of writing) from Nokia which is, or at least was not bundled with my handset.

Download it here

Install the VoIP Settings Manager.  You will find it after installation in Menu > Control Panel > Net Settings > Advanced VoIP Settings. Open the Settings Manager and create a new SIP Profile with the following values:

Profile Name: justvoip
Service Profile: IETF
Default Destination: Internet (I am using VoIP via my Home-WLAN)
Default Access Point:  none
Public Username: sip:YOURJUSTVOIPUSERNAME@justvoip.com (Note: “sip:” will always be added automatically)
Use compression: No
Registration: When needed or always on (choose your preference)
Use Security: No

Proxy & Registration Server have identical(!) values:

Server Address: sip:sip.justvoip.com
Realm: justvoip.com
User name: YOURJUSTVOIPUSERNAME
Password: YOURJUSTVOIPPASSWORD
Allow loose routing: Yes
Transport type: UDP
Port: 5060

After setting up the profile sucessfully, you will be able to activate VoIP from the Homescreen within the same menu, where you activate WLAN scanning. Just select ‘enable justvoip.com’, or how you called the profile, to turn on VoIP. Doing so the VoIP icon appears on your homescreen (Phone with a globe). Selecting a contact  will now feature “Internet call” beside the normal “Voice call” option.

I have just made use of this residing in my home WLAN. Possibly you can also turn VoIP on using a UMTS connection.

Good luck setting this up on your E52 & Happy voiping!

This post in the Nokia Forums helped me setting this all up – please have a look for yourself  if you like.