1. © 2010 Computer Science Faculty, Kabul University ELECTRONICE MAIL CONTINUED… 6 TH LECTURE 9, May, 2010 Baseer Ahmad Baheer

2. © 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.

3. © 2010 Computer Science Faculty, Kabul University

4. 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.

5. © 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.

6. © 2010 Computer Science Faculty, Kabul University POP3

7. © 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)

8. © 2010 Computer Science Faculty, Kabul University

9. IMAP Keep all messages in one place: the server Allows user to organize messages in folders

10. © 2010 Computer Science Faculty, Kabul University

11. 1.telnet mailserver 143 2. login 3. select foldername 4. fetch email number body[text] 5. close 6. logout 1.telnet mailserver 143 2. login 3. select foldername 4. fetch email number body[text] 5. close 6. logout

12. © 2010 Computer Science Faculty, Kabul University

13. References