In the past we've talked about different tactics you can use to track down CEO email addresses. But unfortunately, sometimes they're just next to impossible to find. So when sleuthing doesn't work, it's time to just start guessing. And MailTester helps you confirm your guesses. If you know the format for a particular company's email addresses, such as firstname.lastname@example.org, you can just plug in what you think it might be into MailTester and they'll let you know if you're right. If you don't know the format at all, go to the company's website and check their "contact us" page. From here, you'll at least know the @anycompany.com part and then you can use that to start testing various possibilities. Chances are, you'll eventually hit the right one. Common email formats I've had luck with include:
MailTester works by looking up the SMTP server responsible for the e-mail address, and trying to establish an SMTP connection."It then tries to send several commands, almost as if an e-mail is going to be sent. When enough information is gathered, the connection is aborted."
MailTester isn't successful every time as "some servers only connect to the internet at specified times to retrieve the e-mails that are queued at a secondary SMTP server" and "some SMTP servers don't give any information about the validity of an e-mail address". However, I'd say my success rate using their service is at least 80%.