This volume comprises the systems manuals for two of the most widely used OSI implementations - the X.400 protocols for message handling services, which is actively used in the research industry for gateway and conversion services and the X.500 protocols for directory services, currently the basis of a worldwide pilot in over 14 countries. This book explores the practical problems of implementing X.400 and X.500 services, including the reality of operating and configuring real systems, discusses the merits of alternative design approaches, and outlines the applicability of OSI standards to real world problems, including integration with other systems.