No User Registration/Signup Confirmation Email

I have Pro Sites and Domain Mapping set up w/ EduBlog theme for ezstop.com. There is no confirmation/activation email sent out when end-user sign up from the front-end via http://ezstop.com/wp-signup.php. When I try to create a new site from the Network Admin dashboard, the email sent successfully to new site user email, which seems to indicate that my host email server is working correctly. Please help.