Thanks for this - great to have something as simple to install and use as this, and which doesn't force paid upgrades to extract data etc. Two fairly simple upgrades would give it 5 stars from me:
1. verification that input is actually a valid email address;
2. option to integrate CAPTCHA, e.g. the Really Simple Captcha plugin developed for Contact Form 7, and (I believe) fairly easy to use with other plugins.