Introduction

Users of e-mail systems may be baffled when examining the resources available via the Internet, the global network of networks connecting academia and industry. The Internet was not a well-planned enterprise, but instead arose in more of an "organic" way. In all, the Internet's interconnected and overlapping services may appear to the user as a jungle of incomprehensible and dangerous-looking vines.

This paper is intended as a machete to hack through the Internet jungle.

The paper takes a snapshot of electronic mail and related services that exist in Internet today. The Internet e-mail services refer to all that is necessary to accomplish electronic mail communication among Internet hosts and others.

Internet e-mail services as they exist throughout Internet today are not based on a pre-designed and homogeneous system. Internet e-mail carries a great deal of historic baggage and compromises with itself. As such it has proven to be difficult to understand and manage for the uninitiated. Yet, e-mail is regarded by many as their most valuable application. For these reasons a document such as this can be of value to many.

This document addresses many aspects of Internet e-mail for a wide spectrum of readers. Those who are not familiar with Internet e-mail will find it useful to read this entire document. After reading this document,

SMTP, DNS, MX, UUCP, MMDF, Sendmail, MH, ELM, PEM, MIME, ...

The level of detail provided here is not intended to be sufficient for a system administrator or an end user to solve his problems. This document is primarily intended to be used as a road map, where a general overview of all the significant components is provided and inter-relationships of these components are described. Reference to relevant material where additional detail can be obtained is always provided.