Can you add a settings page to let us add the email that we want to block ?

Thanks for the kind feedback.

A settings option has been suggested a couple of times. I definitely would like to add it one day, and do plan to, but it’s low priority—as the key focus is keeping the plugin as clean and simple as possible to avoid the main spam bots.
If required it is relatively easy to edit the plugin file to add your own list of emails to block.