If it produces an email it is pretty accurate. It checks various possibilities, and returns the valid ones. If only one is returned you can be pretty sure it is

If it produces an email it is pretty accurate. It checks various possibilities, and returns the valid ones. If only one is returned you can be pretty sure it is a valid email. You can use the social links to see if the email is associated to a facebook / twitter account. It does check that the domain is not "catch-all", or that it doesn't simply ignore our queries.