Source: voip-tech.blogspot.com

Yoomba offers an E-Mail VoIP Service, just surf on the Yoomba website, type your E-Mail address, wait for the receipt of the E-Mail message, indispensable to be activated and click on the the link inside the message; afterwards you will be activated and your browser will propose an ActiveX installation, requisite for the usage of Yoomba.
After the short install process and activation you will be notified that all your browser windows and Oulook or Outlook Express windows will be closed to complete the software installation.
Yoomba will import all your Outlook/Outlook Express contacts to allow you to communicate to your contacts that you’re using Yoomba and you can easily communicate with them.
Yoomba is still in beta version and could not be properly stable, being it distributed for free it’s not a pity try it; for the moment it seems not possible to make VoIP calls over landlines phone and cellphones.