Programming Internet Email by David Wood

ISO has established an international standard for electronic mail systems. That standard is X.400. It has a companion standard for directory services (allowing the lookup of names, organizations, etc. over a network) known as X.500.

The X.400 standardization would make an outstanding case study for those interested in decisions by committee. As the new standard progressed, every submitter had to ensure that her pet functionality was represented. Nevertheless, large areas of obvious functionality never made it into the standard, such as facilities for asynchronous access. The X.400 standard was finalized far too late to prevent a raft of commercial vendors from implementing nonstandard systems and seeing their wide deployment.

In the minds of governments worldwide, an ISO standard has the weight of law. Many governments have mandated the use of X.400/X.500 services for their electronic mail systems. This is notwithstanding the fact that many such systems are rather small networks gatewayed to the Internet for long-haul connectivity.

X.400 came into standardization at roughly the same time that the growth of the Internet was causing a huge installed base of SMTP/MIME implementations to be fielded. The PC revolution of the 1980s had already occurred, resulting in many proprietary commercial email systems. In short, X.400 was never widely adopted because it would have required expensive and widespread changes in email systems on a huge scale. That simply never happens.

Contrast ...