This book offers a comprehensive understanding of secure Internet messaging, and brings together all the relevant and critical information needed to use OpenPGP and S/MIME-compliant software. It explores the conceptual and technical approaches followed by the developers of both OpenPGP and S/MIME, and gives a thorough treatment of the latest and most-effective technologies for secure messaging. Ideal for security and network managers, as well as professional system and network administrators, this easy-to-understand book is a complete guide to OpenPGP, S/MIME, Webbased and gateway solutions, certified mail, delivery platforms, and instant messaging.