Yes, here is an example of an address that doesn't exist: https://grepular.com/email_privacy_tester/lookup?code=gapz72l9ox3l95p7&js=1 https://grepular.com/emai

Yes, here is an example of an address that doesn't exist: https://grepular.com/email_privacy_tester/lookup?code=gapz72l9ox3l95p7&js=1 https://grepular.com/email_privacy_tester/lookup?code=gapz72... If the address exists in Gmail, you get a response on "DNS Prefetch - Anchor", so it could be used to determine whether to send an email or not. I'm not a mail administrator but I can imagine how it might be useful to a spammer, e.g to stop mass bounce replies.