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The TCP/IP Guide  9  TCP/IP Application Layer Protocols, Services and Applications (OSI Layers 5, 6 and 7)       9  TCP/IP Key Applications and Application Protocols            9  TCP/IP File and Message Transfer Applications and Protocols (FTP, TFTP, Electronic Mail, USENET, HTTP/WWW, Gopher)                 9  TCP/IP Electronic Mail System: Concepts and Protocols (RFC 822, MIME, SMTP, POP3, IMAP)                      9  TCP/IP Electronic Mail Message Formats and Message Processing: RFC 822 and MIME

TCP/IP Electronic Mail RFC 822 Standard Message Format Processing and Interpretation 1 MIME Message Format Overview, Motivation, History and Standards

The RFC 822 e-mail message format is the standard for the exchange of electronic mail in TCP/IP internetworks. Its use of simple ASCII text makes it easy to create, process and read e-mail messages, which has contributed to the success of e-mail as a worldwide communication method.

Unfortunately, while ASCII text is great for writing simple memorandums and other short messages, it provides no flexibility to support other types of communication. To allow e-mail to carry multimedia information, arbitrary files, and messages in languages using character sets other than ASCII, the Multipurpose Internet Mail Extensions (MIME) standard was created.

In this section I describe MIME and how it is used for modern e-mail messaging. I begin with an overview of MIME and discussion of its history and the standards that define it. I describe the two overall MIME message structures and provide a summary of the important MIME-specific headers. I then explain the important MIME Content-Type header in more detail, and discuss MIME discrete media types, subtypes and parameters. I discuss the more complex MIME multipart and encapsulated message structures, and then the different methods by which data can be encoded into MIME message bodies. I conclude with the special MIME extension to allow support for non-ASCII characters in ordinary e-mail headers.

TCP/IP Electronic Mail RFC 822 Standard Message Format Processing and Interpretation 1 MIME Message Format Overview, Motivation, History and Standards