• 5 htp
• Iana 1
• Mime 1
• S mime

MIME

Table of contents

1 Introduction 2 MIME Headers 2.1 MIME-Version 2.2 Content-type 2.3 Content-Transfer-Encoding 3 Encoded-Word 4 Multipart Example 5 See also 6 References 7 External link

Introduction

The basic format of Internet e-mail is defined in RFC 2822, which is an updated version of RFC 822. These standards specify the familiar formats for text e-mail headers and body and rules pertaining to commonly used header fields such as "To:", "Subject:", "From:", and "Date:". MIME defines a collection of e-mail headers for specifying additional attributes of a message including content type, and defines a set of transfer encodings which can be used to represent 8-bit binary data using characters from the 7-bit ASCII character set. MIME also specifies rules for encoding non-ASCII characters in e-mail message headers, such as "Subject:", allowing these header fields to contain non-English characters.

MIME is extensible. Its definition includes a method to register new content types and other MIME attribute values.

One of the explicit goals of the MIME definition was to not require changes to pre-existing e-mail servers or clients. This goal is achieved by allowing all MIME message attributes to be optional, with default values making a non-MIME message likely to be interpreted correctly by a MIME-capable client. In addition, a simple MIME text message is likely to be interpreted correctly by a non-MIME client although it has e-mail headers the non-MIME client won't know how to interpret.

MIME Headers

  MIME-Version: 1.0

  Content-type: text/plain

Although originally defined for MIME e-mail, the content-type header and MIME type registry is reused in other Internet protocols such as HTTP.

Through the use of the multipart type, MIME allows messages to have parts arranged in a tree structure where the leaf nodes are any non-multipart content type and the non-leaf nodes are any of a variety of multipart types. This mechanism supports:

• simple text messages using text/plain (the default value for "Content-type:")
• text plus attachments (multipart/mixed with a text/plain part and other non-text parts). A MIME message including an attached file generally indicates the file's original name with the "Content-disposition:" header, so the type of file is indicated both by the MIME content-type and the (usually OS-specific) filename extension.
• reply with original attached (multipart/mixed with a text/plain part and the original message as a message/rfc822 part)
• alternative content, such as a message sent in both plain text and another format such as HTML (multipart/alternative with the same content in text/plain and text/html forms)
• many other message constructs

• 7bit - used for US-ASCII text data. This is the default value.
• 8bit - used for 8-bit text data. This can be used only if both the sending and receiving mail transfer agents support the 8bit MIME transport SMTP extension.
• quoted-printable - used for text data consisting primarily of US-ASCII characters
• base64 - used for arbitrary binary data

Multipart Example

Content-type: multipart/mixed; boundary="frontier"
MIME-version: 1.0

--frontier
Content-type: text/plain

This is the body of the message.
--frontier
Content-type: application/octet-stream
Content-transfer-encoding: base64

gajwO4+n2Fy4FV3V7zD9awd7uG8/TITP/vIocxXnnf/5mjgQjcipBUL1b3uyLwAVtBLOP4nV
LdIAhSzlZnyLAF8na0n7g6OSeej7aqIl3NIXCfxDsPsY6NQjSvV77j4hWEjlF/aglS6ghfju
FgRr+OX8QZMI1OmR4rUJUS7xgoknalqj3HJvaOpeb3CFlNI9VGZYz6H6zuQBOWZzNB8glwpC
--frontier--

See also

• DIME — Microsoft has proposed a new technology called DIME which streamlines MIME for use in web services. A specification for the standard has recently been submitted to the Internet Engineering Task Force (IETF).
• S/MIME
• Mailcap

• RFC 2045 - Full text of RFC 2045 Multipurpose Internet Mail Extensions (MIME) Part One: Format of Internet Message Bodies. N. Freed, N. Borenstein. November 1996. (Format: TXT=72932 bytes) (Obsoletes RFC 1521, RFC 1522, RFC 1590) (Updated by RFC 2184, RFC 2231) (Status: DRAFT STANDARD)
• RFC 2046 - Full text of RFC 2046 Multipurpose Internet Mail Extensions (MIME) Part Two: Media Types. N. Freed, N. Borenstein. November 1996. (Format: TXT=105854 bytes) (Obsoletes RFC 1521, RFC 1522, RFC 1590) (Updated by RFC 2646) (Status: DRAFT STANDARD)
• RFC 2047 - Full text of RFC 2047 MIME (Multipurpose Internet Mail Extensions) Part Three: Message Header Extensions for Non-ASCII Text. K. Moore. November 1996. (Format: TXT=33262 bytes) (Obsoletes RFC 1521, RFC 1522, RFC 1590) (Updated by RFC 2184, RFC 2231) (Status: DRAFT STANDARD)
• RFC 2048 - Full text of RFC 2048 Multipurpose Internet Mail Extensions (MIME) Part Four: Registration Procedures. N. Freed, J. Klensin, Jon Postel. November 1996. (Format: TXT=45033 bytes) (Obsoletes RFC 1521, RFC 1522, RFC 1590) (Updated by RFC 3023) (Also BCP0013) (Status: BEST CURRENT PRACTICE)
• RFC 2049 - Full text of RFC 2049 Multipurpose Internet Mail Extensions (MIME) Part Five: Conformance Criteria and Examples. N. Freed, N. Borenstein. November 1996. (Format: TXT=51207 bytes) (Obsoletes RFC 1521, RFC 1522, RFC 1590) (Status: DRAFT STANDARD)

• List of IANA registered MIME Media Types
• List of Character Sets