© 2010 Computer Science Faculty, Kabul University

ELECTRONICE MAIL CONTINUED… 6TH

LECTURE

9, May, 2010 Baseer Ahmad Baheer

© 2010 Computer Science Faculty, Kabul University

The Received Message

• Indeed, the receiving server, appends a Received:

header line to the top of the message; this header line

specifies the name of the SMTP server that sent

• the message ("from"), the name of the SMTP server that

received the message ("by") and the time at which the

receiving server received the message.

© 2010 Computer Science Faculty, Kabul University

© 2010 Computer Science Faculty, Kabul University

• A single message sometimes has multiple Received: header lines

and a more complex Return-Path: header line. This is because a

message may be received by more than one SMTP server in the

path between sender and recipient.

© 2010 Computer Science Faculty, Kabul University

Mail Access Protocols

• There are currently two popular mail access

• protocols: POP3 (Post Office Protocol - Version 3) and IMAP

(Internet Mail Access Protocol).

• POP3 or IMAP are used to transfer mail from the recipient's mail

server to the recipient's user agent.

© 2010 Computer Science Faculty, Kabul University

POP3

© 2010 Computer Science Faculty, Kabul University

• POP3 Uses two different modes:

• Download and delete (cannot re-read email if he changes client)

• Download and Keep (copies of messages on different clients)

© 2010 Computer Science Faculty, Kabul University

© 2010 Computer Science Faculty, Kabul University

IMAP

• Keep all messages in one place: the server

• Allows user to organize messages in folders

© 2010 Computer Science Faculty, Kabul University

© 2010 Computer Science Faculty, Kabul University

1. telnet mailserver 143

2. <tag1> login <username> <password>

3. <tag2> select foldername

4. <tag3> fetch email number body[text]

5. <tag4> close

6. <tag5> logout

© 2010 Computer Science Faculty, Kabul University

© 2010 Computer Science Faculty, Kabul University

References