This Plugin by Reza Moallemi lets you send email messages to individual or a group of commenters. It lets Administrator to see who has wrote more comments on his post and mail to commenters. You can also answer each comment in the admin panel of wordpress by sending a private reply to each commenter.
Latest version 0.7
You you can send private Reply directly from your wordpress admin panel.
Contact commenters form added as a submenu to the edit-comments page.
Download and infi: http://wordpress.org/extend/plugins/contact-commenter/
