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Authors:
James F. Kurose, Keith W. Ross
Chapter:
Application Layer
Exercise:
Review
Question:17 | ISBN:9780132856201 | Edition: 6

Question

Print out the header of an e-mail message you have recently received. How many Received: header lines are there? Analyze each of the header lines in the message.

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Answer

Received: 
from 65.54.246.203 (EHLO bay0-omc3-s3.bay0.hotmail.com) (65.54.246.203) by mta419.mail.mud.yahoo.com with SMTP; Sat, 19 May 2007 16:53:51 -0700 
Received: 
from hotmail.com ([65.55.135.106]) by bay0-omc3-s3.bay0.hotmail.com with Microsoft SMTPSVC(6.0.3790.2668); Sat, 19 May 2007 16:52:42 -0700 
Received: 
from mail pickup service by hotmail.com with Microsoft SMTPSVC; Sat, 19 May 2007 16:52:41 -0700 Message-ID: <BAY130-F26D9E35BF59E0D18A819AFB9310@phx.gbl> 
Received: from 65.55.135.123 by by130fd.bay130.hotmail.msn.com with HTTP; Sat, 19 May 2007 23:52:36 GMT From: "prithula dhungel" <prithuladhungel@hotmail.com> 
To: prithula@yahoo.com 
Bcc: 
Subject: Test mail 
Date: Sat, 19 May 2007 23:52:36 +0000 Mime-Version: 1.0 
Content-Type: Text/html; format=flowed 
Return-Path: prithuladhungel@hotmail.com 
Figure: A sample mail message header 
Received: This header field indicates the sequence in which the SMTP servers send and receive the mail message including the respective timestamps. In this example there are 4 "Received:" header lines. This means the mail message passed through 5 different SMTP servers before being delivered to the receiver's mail box. The last (forth) "Received:" header indicates the mail message flow from the SMTP server of the sender to the second SMTP server in the chain of servers. The sender's SMTP server is at address 65.55.135.123 and the second SMTP server in the chain is by130fd.bay130.hotmail.msn.com. The third "Received:" header indicates the mail message flow from the second SMTP server in the chain to the third server, and so on. Finally, the first "Received:" header indicates the flow of the mail messages from the forth SMTP server to the last SMTP server (i.e. the receiver's mail server) in the chain. 
Message-id: The message has been given this number BAY130- F26D9E35BF59E0D18A819AFB9310@phx.gbl (by bay0-omc3-s3.bay0.hotmail.com. Message-id is a unique string assigned by the mail system when the message is first created. 
From: This indicates the email address of the sender of the mail. In the given example, the sender is "prithuladhungel@hotmail.com" 
To: This field indicates the email address of the receiver of the mail. In the example, the receiver is "prithula@yahoo.com" 
Subject: This gives the subject of the mail (if any specified by the sender). In the example, the subject specified by the sender is "Test mail" 
Date: The date and time when the mail was sent by the sender. In the example, the sender sent the mail on 19th May 2007, at time 23:52:36 GMT. 
Mime-version: MIME version used for the mail. In the example, it is 1.0. 
Content-type: The type of content in the body of the mail message. In the example, it is "text/html". 
Return-Path: This specifies the email address to which the mail will be sent if the receiver of this mail wants to reply to the sender. This is also used by the sender's mail server for bouncing back undeliverable mail messages of mailer-daemon error messages. In the example, the return path is "shreejaymall97@gmail.com".

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