I think WP already sends email to the post author if someone lefts a comment on his post.

It doesn’t seem to support custom post types. I was hoping your plugin would solve this issue though.

So you are saying WP doesn’t send emails for custom post type comment?

That’s correct. The admins receive emails, but the author doesn’t.

In the WordPress discussion settings if you have the first one checked, the post author always gets the email..

For the second one, if any comment is not approved, it sends an email to the admin.

Also sending approved comments to the admin, you can use this snippet:
[php]
function wpufe_notify_comment( $comment_ID, $approved ) {
if ( $approved != ‘0’ ) {
wp_notify_moderator( $comment_ID );
}
}

add_action( ‘comment_post’, ‘wpufe_notify_comment’, 10, 2 );
[/php]