In https://github.com/Gradberry/Email-Permutator/blob/master/smtp_validateEmail.class.php https://github.com/Gradberry/Email-Permutator/blob/master/sm... it loo

In https://github.com/Gradberry/Email-Permutator/blob/master/smtp_validateEmail.class.php https://github.com/Gradberry/Email-Permutator/blob/master/sm... it looks like they are validating the recipients by starting to send an email, then reset the connection after the recipients email address get accepted or rejected. Dos that old trick still work? I thought that (at least the big guys) quickly banned an ip address trying this. And if they don't this may be a good time to start!