Email Notification of Threaded Comment Replies

Hey Gang,

Is it possible for an email notification to be sent automatically when someone replies to a threaded comment (to the person who left the original comment) even if they have not opted to “subscribe to comments” with email?

I was using IntenseDebate, and it works that way – if you leave a comment on a blog, and then the author (or someone else) leaves a reply to your comment, you’d get an email saying “*** responded to your comment on …. “. This would happen REGARDLESS of whether or not you checked the “follow comments via email” option with IntenseDebate.

With the WordPress version of threaded comments, I have tested it, and though you can thread comments and leave a reply, none of the people know about it unless they happen to come back over to your blog.

I’m torn – IntenseDebate isn’t syncing my comments as it should, but it works pretty well … and I’ve gotten a LOT more discussion by using it. However, I’d rather keep all my comments locally on my server, but the WordPress threaded comment structure does not send email notifications of responses … at least, that I’m aware of.

Anyone know if I’m missing anything, or if this can be done?
Fred