Secure Multipurpose Internet Mail Extensions S-MIME <messaging, standard> (S-MIME) A specification for secure {electronic mail}. S-MIME was designed to add security to e-mail messages in {MIME} format. The security services offered are {authentication} (using {digital signatures}) and {privacy} (using {encryption}). (http://rsa.com/rsa/S-MIME/). (1997-05-10)