Hi Armin,

You can disable the new user registration notification email in your site settings (Advanced Settings - Registration Settings - Receive User Registration Notification). As for general notification emails, most are sent by different sub-systems or modules reacting to various events, so, I don't know of a way to turn all of them off. With that said, in your site settings, when you're logged into the host account, you can go to "Messaging Settings" and turn off "Send Emails" - that, I believe, will disable DNN's standard notification emails from the social system.

Hope this helps,

Mike