Subscribe to authors post

I put together a site for a client with 10 authors, he wants people to be able to subscribe to authors post by email, so if they only want say the #3 author, they would only get updates from his or her post instead of all blog post.

I found this plugin but its for rss feed by author.. Anyone know of another plugin that allows someone to subscribe by email per author..

Subcribe2 looks like it will allow the person to select categories but they have to be registered user of the site..

Thanks Scott