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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
9 TCP/IP Electronic Mail Standard Message Format: RFC 822
TCP/IP Electronic Mail RFC 822 Standard Message Format Header Field Definitions and Groups
(Page 1 of 3)
822 message format describes the structure
and content of TCP/IP e-mail messages. The structure is intentionally
designed to be very simple and easy to both create and understand. Each
message begins with a set of headers that describe the message and its
contents. An empty line marks the end of the headers, and then the message
The message body contains the actual
text that the sender is trying to communicate to the recipient(s), while
the message header contains various types of information that serve
various purposes. The headers help control how the message is processed,
by specifying who the recipients are, describing the contents of the
message, and providing information to a recipient of a message about
processing done on the message as it was delivered.
Header Field Structure
Each header field follows the simple
text structure we saw in the preceding topic:
<header name>: <header
The <header name> is of course
the name of the header, and the <header value> is the value associated
with that header, which depends on the header type. Like all RFC 822
lines, headers must be no more than 998 characters long and are recommended
to be no more than 78 characters in length, for easier readability.
The RFC 822 and 2822 standards support a special syntax for allowing
headers to be folded onto multiple lines if they are very
lengthy. This is done by simply continuing a header value onto a new
line, which must begin with at least one white space
character, such as a space or <Tab> character, like this:
<header name>: <header
value part 1>
<white space> <header value part 2>
<white space> <header value part 3>
The <Tab> character is most
often used for this purpose. So, for example, if we wanted to specify
a large number of recipients for a message, we could do it as follows:
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The TCP/IP Guide (http://www.TCPIPGuide.com)
Version 3.0 - Version Date: September 20, 2005
© Copyright 2001-2005 Charles M. Kozierok. All Rights Reserved.
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