emailnotification: no admin backend?

WordPress, even without a plugin, will email you when someone registers. See this:
http://codex.ww.wp.xz.cn/General_Options_SubPanel

Users and Authors can be managed in your Admin Panel. See this:
http://codex.ww.wp.xz.cn/Authors_and_Users_SubPanel

You might also be interested in the options regarding Comments (discussion):
http://codex.ww.wp.xz.cn/Discussion_Options

helmer; I didn’t install the Word Press Email Notification Plugin but it seems that plugin requires the creation on the MySQL table called “email_list” in your WordPress database. Maybe use phpMyAdmin to at least look at the records of that table as it likely has those users.

Guess you call that a poor man’s admin 😉 Hope that helps.