User manual approval and deny option after they sign up

Hello guys,

Is there any option for admin to approve and unapproved user manually from the admin users section. I want all users to be unapproved by default when they sign up and when the sign up they just get an onscreen message, client is notified by mail to approve user.

Is there any extension or plugin in wpmu from which i can achieve this. I just want to check all users before they start using the website.