1. School of Electronics and Telecommunications 1/25 Presented by: Pham Van Chi Bui Thi The Ha Electronic Mail: SMTP

2. School of Electronics and Telecommunications 2/25 OBJECTIVES:  To explain the architecture of electronic mail using four scenarios.  To explain the user agent (UA)  Transfer Protocol (SMTP) as the formal protocol that handles MTA.  To explain e-mail transfer phases.

3. School of Electronics and Telecommunications 3/25 Explain the architecture of electronic mail To explain the architecture of email, we give four scenarios Scenarior 1 Scenarior 2 Scenarior 3 Scenarior 4

4. School of Electronics and Telecommunications 4/25 Figure 1 First scenario

5. School of Electronics and Telecommunications 5/25 When the sender and the receiver of an e- mail are on the same mail server, we need only two user agents. Note:

6. School of Electronics and Telecommunications 6/25 Figure 2 Second scenario

7. School of Electronics and Telecommunications 7/25 When the sender and the receiver of an e- mail are on different mail servers, we need two UAs and a pair of MTAs (client and server). Note:

8. School of Electronics and Telecommunications 8/25 Figure 3 Third scenario

9. School of Electronics and Telecommunications 9/25 When the sender is connected to the mail server via a LAN or a WAN, we need two UAs and two pairs of MTAs (client and server). Note:

10. School of Electronics and Telecommunications 10/25 Figure 4 Fourth scenario

11. School of Electronics and Telecommunications 11/25 When both sender and receiver are connected to the mail server via a LAN or a WAN, we need two UAs, two pairs of MTAs (client and server), and a pair of MAAs (client and server). This is the most common situation today. Note:

12. School of Electronics and Telecommunications 12/25 Figure 5 Push versus pull

13. School of Electronics and Telecommunications 13/25 Explain the user agent (UA), - UA là thành phần đầu tiên của một hệ thống thư điện tử - Cung cấp dịch vụ tới người sử dụng - Giúp quá trình gửi nhận thư dễ dàng hơn

14. School of Electronics and Telecommunications 14/25 Figure 6 User agent Some examples of command-driven user agents are mail, pine, and elm Some examples of GUI-based user agents are Eudora, Outlook, and Netscape Note:

15. School of Electronics and Telecommunications 15/25 Transfer Protocol (SMTP) - Để gửi mail, hệ thống phải có client MTA - Để nhận mail. Hệ thống phải có server MTA - Giao thức định nghĩa MTA client và server trên Internet được gọi là SMTP (Simple Mail Transfer Protocol) - Scenario 4 là trường hợp thường gặp nhất - Hình 7 thể hiện phạm vi sử dụng giao thức SMTP trong scenario này

16. School of Electronics and Telecommunications 16/25 Figure 7 SMTP range

17. School of Electronics and Telecommunications 17/25 Figure 8 Commands and responses command/response interaction – commands: ASCII text – response: status code and phrase messages must be in 7-bit ASCII Uses CRLF.CRLF to determine end of message

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20. School of Electronics and Telecommunications 20/25 Figure 9 Message transfer

21. School of Electronics and Telecommunications 21/25 Figure 10 Connection termination

22. School of Electronics and Telecommunications 22/25 Send A Fake Mail uses QK SMTP server -Sử dụng TELNET để login cổng 25 (the well-known port for SMTP). - Sử dụng câu lệnh để gửi email. - Giả sử billg@microsoft.com gửi 1 email cho chipvc@gmail.comchipvc@gmail.com Example

23. School of Electronics and Telecommunications 23/25 23 Example Example Continued ================== Connection Establishment ================ 220 Welcome to QK SMTP Server 3 helo hacker (Type helo & any name followed by space) 250 Hello hacker (Server Welcomes You) ===================== Envelope =================== MAIL FROM: billg@microsoft.com 250 billg@microsoft.com Address Okay (Server gives a positive response) RCPT TO: chipvc@gmail.combillg@microsoft.com chipvc@gmail.com 250 chipvc@gmail.com Address Okay =================== Header and Body ================== DATA (type this command to start input data) 354 Please start mail input From:Gates To:chipvc@gmail.com Date:Sat Jan 5,2008 9:45 PM Subject:Test to send fake emailchipvc@gmail.combillg@microsoft.com

24. School of Electronics and Telecommunications 24/25 Figure 11 SMTP, Pop3 and IMAP4

25. School of Electronics and Telecommunications 25/25 Any