[Register Plus] No confirmation emails

There are already some topics about this issue. Some are solved others not. So I decided to see if this works in my case.

I installed this plugin registered a new user, manually approved him in the admin area. The result: The user has not received the mail but the mail to the admin was sent out.

I reactivated the plugin, new user registration: same negative result.
I reinstalled the plugin, new user registration: same negative result.
Both steps done with other plugins deactivated.

Any suggestions?