FYI @rbarnes305, this plugin, and Easy SMTP and Mailbank and most of the others on here all use PHPMailer underneath. PHPMailer is what handles the encryption. Not the plugins.
There are a few plugins that don't use PHPMailer, they are Postman (Zend), Cimy (Swift), WP Mandrill (Mandrill API) and SendGrid (SendGrid API).