About SSL/TLS

SSL/TLS enables you to communicate securely with your server. Most of the major protocols such as http, smtp, pop3, imap can use SSL/TLS. While TLS can be used over the same port, SSL has to be run on a different port such as https, smtps, pop3s, imaps. SSL has been superseded by TLS. You can find more information about SSL/TLS on Wikipedia.

StartCom Free SSL Certification Authority and CAcert.org are two CAs which issue free certificates.