Please Whitelist This Site?

I know everyone hates ads. But please understand that I am providing premium content for free that takes hundreds of hours of time to research and write. I don't want to go to a pay-only model like some sites, but when more and more people block ads, I end up working for free. And I have a family to support, just like you. :)

If you like The TCP/IP Guide, please consider the download version. It's priced very economically and you can read all of it in a convenient format without ads.

If you want to use this site for free, I'd be grateful if you could add the site to the whitelist for Adblock. To do so, just open the Adblock menu and select "Disable on tcpipguide.com". Or go to the Tools menu and select "Adblock Plus Preferences...". Then click "Add Filter..." at the bottom, and add this string: "@@||tcpipguide.com^$document". Then just click OK.

Thanks for your understanding!

Sincerely, Charles Kozierok
Author and Publisher, The TCP/IP Guide


NOTE: Using software to mass-download the site degrades the server and is prohibited.
If you want to read The TCP/IP Guide offline, please consider licensing it. Thank you.

The Book is Here... and Now On Sale!

Read offline with no ads or diagram watermarks!
The TCP/IP Guide

Custom Search







Table Of Contents  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

Previous Topic/Section
TCP/IP Electronic Mail RFC 822 Standard Message Format Header Field Definitions and Groups
Previous Page
Pages in Current Topic/Section
1
2
Next Page
TCP/IP Enhanced Electronic Mail Message Format: Multipurpose Internet Mail Extensions (MIME)
Next Topic/Section

TCP/IP Electronic Mail RFC 822 Standard Message Format Processing and Interpretation
(Page 1 of 2)

The standards that define SMTP describe the protocol as being responsible for transporting mail objects. A mail object is described as consisting of two components: a message and an envelope. The envelope contains all the information necessary to accomplish transport of the message; the message is everything in the e-mail message we have seen in the last two topics, including both message header and body.

The distinction between these is important technically. Just as the postal service only looks at the envelope and not its contents in determining what to do with a letter—no wise-cracks, please! J—SMTP likewise only looks at the envelope in deciding how to send a message. It does not rely on the information in the actual message itself for basic transport purposes.

So technically, the envelope is not the same as the message headers. However, as you can tell by looking at the list of e-mail headers, each message includes the recipients and other information needed for mail transport anyway. For this reason, it is typical for an e-mail message to be specified with sufficient header information that it can be considered enough by itself to accomplish its own delivery. E-mail software can process and interpret the message to construct the necessary “envelope” for SMTP to transport the message to its destination mailbox(es). The distinction between an e-mail message and its envelope is discussed in more detail in the topic describing SMTP mail transfers.


Previous Topic/Section
TCP/IP Electronic Mail RFC 822 Standard Message Format Header Field Definitions and Groups
Previous Page
Pages in Current Topic/Section
1
2
Next Page
TCP/IP Enhanced Electronic Mail Message Format: Multipurpose Internet Mail Extensions (MIME)
Next Topic/Section

If you find The TCP/IP Guide useful, please consider making a small Paypal donation to help the site, using one of the buttons below. You can also donate a custom amount using the far right button (not less than $1 please, or PayPal gets most/all of your money!) In lieu of a larger donation, you may wish to consider purchasing a download license of The TCP/IP Guide. Thanks for your support!
Donate $2
Donate $5
Donate $10
Donate $20
Donate $30
Donate: $



Home - Table Of Contents - Contact Us

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.
Not responsible for any loss resulting from the use of this site.