ITPEC IP April 2023 Question 30
Topic: Networks
Which of the following is an appropriate combination of the protocols that are used for transmitting and receiving e-mail as shown in the diagram below?
Explanation
(1) SMTP, (2) POP3, (3) SMTP — SMTP pushes mail toward the recipient's mailbox, and POP3 lets the client fetch it from there.
- •(1) Send — the mail client hands the message to its mail server by SMTP (Simple Mail Transfer Protocol).
- •(3) Transfer — the sender's mail server relays the message to the recipient's mail server, again by SMTP.
- •(2) Receive — the client downloads the messages stored in its mailbox on the server by POP3 (Post Office Protocol version 3). IMAP4, which keeps the mail on the server, is the alternative.
Answer (c)
Why not others:
- •(a) POP3, POP3, SMTP — POP3 only retrieves mail from a mailbox; it cannot send a message
- •(b) POP3, SMTP, POP3 — swaps every role: sending and server-to-server transfer are SMTP's job, receiving is POP3's
- •(d) SMTP, SMTP, SMTP — SMTP delivers mail to a server; a client collecting its own mail uses POP3 or IMAP4
Key rule: SMTP is used for every step that pushes mail forward, client to server and server to server; POP3 or IMAP4 only for the client pulling mail from its mailbox.
Networks · AI-written, may contain errors
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