GATE CS 2011 Q.4 (CS Q.4): Application Layer: DNS, HTTP, SMTP, FTP

Consider different activities related to email.

$m_1$ : Send an email from a mail client to a mail server

$m_2$ : Download an email from mailbox server to a mail client

$m_3$ : Checking email in a web browser

Which is the application level protocol used in each activity?

$m_1$ : HTTP, $m_2$ : SMTP, $m_3$ : POP

$m_1$ : SMTP, $m_2$ : FTP, $m_3$ : HTTP

$m_1$ : SMTP, $m_2$ : POP, $m_3$ : HTTP

$m_1$ : POP, $m_2$ : SMTP, $m_3$ : IMAP

Official answer and solution

Solution

Identify the standard application-layer protocols used for mail submission, mail retrieval, and web-based email access.

Sending an email from a client (User Agent) to an outgoing Mail Transfer Agent (MTA) uses the Simple Mail Transfer Protocol (SMTP).

Downloading emails from a mail server mailbox to a local mail client uses Post Office Protocol version 3 (POP3) or Internet Message Access Protocol (IMAP). Here POP is listed.

Accessing webmail through a standard web browser uses the HyperText Transfer Protocol (HTTP).

Final answer

The answer is the one in the official GATE answer key. The solution is this site's own explanation.

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