Secure Sockets Layer (SSL) and Transport Layer Security (TLS), its successor, are cryptographic protocols which provide secure communications on the Internet for such things as e-mail, Internet faxing, and other data transfers. There are slight differences between SSL 3.0 and TLS 1.0, but the protocol remains substantially the same.

     source - Transport Layer Security. (2006, August 31). In Wikipedia, The Free Encyclopedia. Retrieved September 3, 2006, from http://en.wikipedia.org/wiki/Transport_Layer_Security

It is important to remember that standard email protocols (POP3, IMAP4, and SMTP) all communicate natively unencrypted over well-known ports and are inherently insecure. Recent developments in security have added the ability to encrypt such transmissions using TLS (Transport Layer Security) over the same standard TCP ports. Hautspot recommends the use of TLS (when supported by the client's mail service provider) for added security.