MIME and mail

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Contents 1 MIME 2 Mail 3 MIME types 4 'MIME compatible' 5 See also

MIME

MIME (Multipurpose Internet Mail Extensions) is a container format mostly commonly used in mail sent over SMTP.

(The combination is sometimes called SMTP/MIME, but this is often avoided to avoid confusion with S/MIME, a public-key scheme that allows the signing and encrypting of MIME messages)

MIME deals with text coding (character set specification, and non-ASCII headers), but also with message structure, particularly multi-part bodies, which allows attachments (text and non-text), and message nesting (useful in replying and forwarding messages verbatim, including attachments).

See also Binary-to-text coding#Base64 and Binary-to-text coding#Quoted Printable

Mail

MIME types

'MIME type' is now called Internet media type.

'MIME compatible'

Specific parts of MIME-formatted messages may not contain certain characters, which means things like control characters (0x00-0x1F, 0x7F), and non-ASCII (0x80-0xFF)(verify).

Some characters (like 0x0D, 0x0A) may be parsed out.

As a result:

• binary data cannot be safely embedded as-is, and must be encoded using Base64, which is a simple transformation of binary data into printable ASCII characters (similar to as do uuencode, binhex), taking more space in the process.

• some character codings cannot be used. For example, For example, SCSU cannot be used in MIME (without also Base64ing it, which would negate much of its coding efficiency).

See also

• http://en.wikipedia.org/wiki/MIME
• http://www.iana.org/assignments/media-types/

Standards:

• RFC 2821: 'Simple Mail Transfer Protocol)' (SMTP)
• RFC 2822: 'Internet Message Format' (mostly outdates RFC 822)
• RFC 822: 'Standard for the Format of ARPA Internet Text Messages'

And also:

• RFC 2045: 'MIME Part One: Format of Internet Message Bodies'
• RFC 2046: 'MIME Part Two: Media Types'
• RFC 2047: 'MIME Part Three: Message Header Extensions for Non-ASCII Text'

• RFC 2231: 'MIME Parameter Value and Encoded Word Extensions: Character Sets, Languages, and Continuations'

Also related, perhaps a little less interesting:

• RFC 4288: 'Media Type Specifications and Registration Procedures'
• RFC 4289: 'MIME Part Four: Registration Procedures'
• RFC 2077: 'The Model Primary Content Type for Multipurpose Internet Mail Extensions'