Outlook expert Sue Mosher maintains what must be the most comprehensive Outlook-oriented site on the Web at http://www.slipstick.com . In particular, her write-up of the management options for the Outlook E-Mail Security Update (see http://www.slipstick.com/outlook/esecup/admin.htm ) is a great summary of how to make the product do what you want it to do.
The Microsoft Office Resource Kit site has complete information on the Outlook security package, setting up RPC over HTTP, using IRM, and other Outlook security topics. See http://www.microsoft.com/office/ork/2003/three/default.htm .
For more information on the Windows RMS package, see its page at http://www.microsoft.com/rms .
To learn more than you ever wanted to know about S/MIME algorithms, protocols, and implementation considerations, visit the S/MIME Working Group of the Internet Engineering Task Force (IETF) at http://www.imc.org/ietf-smime/index.html .