MIME

Multipurpose Internet Mail Extensions (MIME) is an Internet Standard for the format of e-mail. Virtually all Internet e-mail is transmitted via SMTP in MIME format. Internet e-mail is so closely associated with the SMTP and MIME standards that it is sometimes called SMTP/MIME e-mail.

Introduction

The basic Internet e-mail transmission protocol, SMTP, supports only 7-bit ASCII characters (see also 8BITMIME).

Related Topics:
ASCII - 8BITMIME

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This effectively limits Internet e-mail to messages which, when transmitted, include only the characters used for the English language.

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MIME defines mechanisms for sending other kinds of information in e-mail, including text in languages other than English using character encodings other than ASCII as well as 8-bit binary content such as files containing images, sounds, movies, and computer programs. MIME is also a fundamental component of communication protocols such as HTTP, which requires that data be transmitted in the context of e-mail-like messages, even though the data may not actually be e-mail.

Related Topics:
Character encoding - Image - Sound - Movie - Computer program - HTTP

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Mapping messages into and out of MIME format is typically done automatically

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by an email client or by

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proprietary mail servers when sending or receiving Internet (SMTP/MIME) e-mail.

Related Topics:
Proprietary - Mail server

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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:".

Related Topics:
RFC - Headers

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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.

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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.

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

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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.

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