Secure Socket Layer (SSL) is a technology that helps you secure communication between a browser client and a server. If you consider email security, an SSL makes sure that no data in your mail is exposed to MITM during the transit. There are two primary purposes for which you can use SSL certificates in email: Authenticate and verify the identity of the sender Maintain the integrity of email content One of the most important use cases for an SSL certificate in email security is ensuring that your communication with the mail server is secure. Hackers can take control of the mail server and access your emails.