I had an idea for a similar product a while back which would be basically the same thing for group messaging on mobile phones.
This could be a great tool for those business founders that need to send a flood of emails quickly.
Yep. There's plenty of services that do it, Jeff just built this for me because I was being stubborn and didn't want to fork out the money.
It seemed like a good use for Mustache. It's for sending a few hundred emails in your normal client. Also a nice tool for learning the template language.