s-mime

from The Free On-line Dictionary of Computing (8 July 2008)

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)

from V.E.R.A. -- Virtual Entity of Relevant Acronyms (June 2006)

SMIME
       Secure/Multipurpose Internet Mail Extensions (MIME, MS, Lotus,
Qualcomm, RSA, cryptography), "S/MIME"