This is a good idea and would be a really useful service, but doing it this way doesn't work. What the app is doing is using SMTP to try various permutations of

This is a good idea and would be a really useful service, but doing it this way doesn't work. What the app is doing is using SMTP to try various permutations of the name to see if the email is rejected or accepted by the email server. The problem is that almost every email server is configured to return false data for spam protection. If you want to see the process in more detail, you can look at http://centralops.net/co/ http://centralops.net/co/ which will make the queries directly. One could use the google API to make a better version of this with more intelligence. Often you can use google to find email addresses of a company's employees with some educated guessing, or you can at least figure out the format (eg firstname.lastname@example.com). As it stands this current version only works with perhaps 1 in 5 or 10 domains.