Email comments to authors

Very frustrating that no one has responded.
However, I’ve read that wordpress should do this by default. That is, Author A should be getting notified of comments. However, it seems as though this is not always the case. I’m not sure why our authors would not be getting notified.

Looks like this is one plug-in that does it:
http://wordpress.org/extend/plugins/notify-on-comment/

Do we need a plug-in? Or is there a way for WP to send comments to blog post authors automatically?