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Understanding TCP/IP

You're reading from   Understanding TCP/IP A clear and comprehensive guide to TCP/IP protocols

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Product type Paperback
Published in May 2006
Publisher Packt
ISBN-13 9781904811718
Length
Edition 1st Edition
Concepts
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Author (1):
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CP Books a.s. CP Books a.s.
Author Profile Icon CP Books a.s.
CP Books a.s.
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Toc

Table of Contents (20) Chapters Close

Preface 1. Introduction to Network Protocols FREE CHAPTER 2. Network Monitoring Tools 3. Physical Layer 4. Link Layer 5. Internet Protocol 6. IP Address 7. Routing 8. IP Version 6 9. Transmission Control Protocol 10. User Datagram Protocol 11. Domain Name System 12. Telnet 13. File Transfer Protocol 14. Hypertext Transfer Protocol 15. Email 16. Forums 17. Lightweight Directory Access Protocol A. CISCO Routers Index

15.2 Mail Message Format

The mail message format is specified by the RFC 822 standard. Every email message contains a message header and a message body. The message header is separated from the message body by one blank line (CR LF CR LF). The header and the body of the message use only ASCII characters.

The header is formed from individual header fields. Every header field begins with a keyword followed by a colon. Parameters can be listed after the keyword. The header field ends at the end of a line (i.e., CR LF).

Spaces and tabs may be inserted between individual parts of the header field. The header field may continue on the next line. However, in such a case, the next line must begin with a space or tab (the keyword of the header field must be indented from the first position in the line).

The following characters have special significance, especially in an address:

  • Semicolon (;) and colon (:) are important list delimiters. A colon follows the field name and, for example, semicolons separate...
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