When we first launched ESP Finder it could identify a small group of ESPs, took about 10-20 seconds to reply, and was based on a very basic set of rules. Even still it's been used tens of thousands of times by thousands of marketers. Now, two and a half years later, it can identify more than 140 different ESPs, usually takes less a few seconds seconds to reply, and is based on more than 220 rules to give super accurate results. It's still free, we still use it ourselves almost every day, and hope this update will make it an every more useful tool for marketers everywhere. Enjoy!

Thanks @Gregg & team :)