Set email notification to "no" as per default for new users

Hi,

I need to change the default value for email notification to no instead of yes. Because of the missing option to do so could you give me a hint where to start at?

I want to have all email notifications activated at the backend but for default for each user it should be off. So if people like to have email notificationsthey can easily put the switch from no to yes in their notification area in the frontend.

But the moment I activated all email notifications, people got tons of emails because the settings went to on for all members. This is mega bad! Many members got around 70 mails for one day. I need to have this option set to no for default.