School of Electronics and Telecommunications 1/25 Presented by: Pham Van Chi Bui Thi The Ha Electronic Mail: SMTP
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 transfer phases.
School of Electronics and Telecommunications 3/25 Explain the architecture of electronic mail To explain the architecture of , we give four scenarios Scenarior 1 Scenarior 2 Scenarior 3 Scenarior 4
School of Electronics and Telecommunications 4/25 Figure 1 First scenario
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:
School of Electronics and Telecommunications 6/25 Figure 2 Second scenario
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:
School of Electronics and Telecommunications 8/25 Figure 3 Third scenario
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:
School of Electronics and Telecommunications 10/25 Figure 4 Fourth scenario
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:
School of Electronics and Telecommunications 12/25 Figure 5 Push versus pull
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
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:
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
School of Electronics and Telecommunications 16/25 Figure 7 SMTP range
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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School of Electronics and Telecommunications 20/25 Figure 9 Message transfer
School of Electronics and Telecommunications 21/25 Figure 10 Connection termination
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 . - Giả sử gửi 1 cho Example
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: 250 Address Okay (Server gives a positive response) RCPT TO: 250 Address Okay =================== Header and Body ================== DATA (type this command to start input data) 354 Please start mail input From:Gates Date:Sat Jan 5,2008 9:45 PM Subject:Test to send fake
School of Electronics and Telecommunications 24/25 Figure 11 SMTP, Pop3 and IMAP4
School of Electronics and Telecommunications 25/25 Any