1. Introduction

The first and second documents in this set define MIME header fields and the initial set of MIME media types. The third document describes extensions to RFC 822^std11(-> 2822^prop) formats to allow for character sets other than US-ASCII. This document describes what portions of MIME must be supported by a conformant MIME implementation. It also describes various pitfalls of contemporary messaging systems as well as the canonical encoding model MIME is based on.