HOW WE CHECK IF AN EMAIL IS SECURE
When you enter an email in the Secure Email Checker, we look to see if the email server supports inbound Transport Layer Security (TLS) encryption.
If the email server supports TLS encryption, that means any message you send to that email address can’t be snooped and is protected in transit.
When you enter an email, we check the first three MX records with the highest priority. Some email providers use multiple MX records tied to servers with different levels of TLS support.
If all MX records show the same priority, we randomly select three. If the results show MX records with the same priority, then run the check a few times to improve the accuracy of results.