Defines and discusses the requirements for Internet host software and covers the application and support protocols.

Defines the general structure of the MIME media typing system and defines an initial set of media types.

Specifies the syntax for Internet mail text messages.

Specifies the format of Internet message bodies and the various headers used to describe the structure of MIME messages.

Describes extensions to RFC 822 to allow non-US-ASCII text data in Internet mail header fields.

Specifies various IANA registration procedures for MIME media types, MIME external body access types, and MIME content-transfer-encodings.

Describes how mail systems on the Internet are expected to route messages based on information from the domain system.

Describes the widely implemented Simple Mail Transfer Protocol (SMTP) designed to transfer mail reliably and efficiently and relay mail across transport service environments.

Describes MIME conformance criteria as well as providing some illustrative examples of MIME message formats.

Defines a framework for extending the SMTP service by defining a means whereby a server can inform a client as to the service extensions it supports.