White and Blacklist Emails
The Email Whitelister plugin has been updated to v1.01 to fix several bugs faced by people.
Also due to popular demand, I've released the Email Blacklister plugin which functions exactly like the Whitelister except it junks comments if the email address entered matches one on the blacklist. Currently the plugin is fairly basic and doesn't allow you to enter any wildcard or regex values. A future version will hopefully contain such functionality.