I installed the plugin from what I believe is your site:
When I isntalled it and try to go to the admin site I get:
Fatal error: Cannot redeclare wp_notify_postauthor() (previously declared in /hermes/waloraweb057/b299/moo.alquilacl/wp-includes/pluggable.php:988) in /hermes/waloraweb057/b299/moo.alquilacl/wp-content/plugins/comment-emailer/notify_postauthor.php on line 147
Did I do something wrong? I would live your help with this, please and thank you.