Content Monitor Plugin is not working

I installed this plug and it’s not sending emails when words in the list are included in the post. I’ve added my word list and enabled the plugin. The activation/welcome emails work, so I know that email in general is working. Any tips to configure? The apache error_log has these lines:

sh: 1: /usr/bin/sendmail: not found

Can it be configured to use wordpress email (vs. sendmail)?