About MIME Formatting

Multipurpose Internet Mail Extension (MIME) is a specification for formatting non-ASCII message that enables the transfer and acceptance of files over the Internet. MIME-compliant messages can contain multiple data types, for example:

• Text messages in US-ASCII format

• Messages of unlimited length

• Binary files

• Character sets other than US-ASCII

• Multimedia: image, audio, and video objects

• Multiple, nested objects in a single message

MIME is a two-part message format with a header and a body. The header metadata provides the information for message transmission and interpretation. The body contains the bulk data. MIME messages can remain in binary format when transmitted over a protocol such as HTTP or FTP.

However, if a MIME message is sent by SMTP or another text-only protocol, is must be base64 encoded (base64 encoding is a text-based representation of binary data). For more information, see the Internet Engineering Task Force Text Messages specification (RFC 822) and the MIME Message Body Format (RFC 2045), at http://www.ietf.org.

The S/MIME Version 3 specification (RFC 2623) is also found at the same URL.