Follow Blogs and Email Notifications for comments

Hi - Is there any plugin that I can install on my wordpress multisite so that bloggers on my network can follow blogs, if they comment on any blog they become subscribed to that post and if anyone post new comments, they get email notification?

I want non registered commenters to be subscribed to posts they comment on and get emails on new comments.

Can we not get the follow option which is available on wordpress.com?

Any suggesting is highly appreciated.

Thanks,
Jamshid