GATE CS 2011 Q4 — Application Layer Protocols: DNS, SMTP, HTTP, FTP, Email

To identify the correct application layer protocols for each activity, let us analyze their functions:

• $\text{m1}$: Sending an email from a mail client to a mail server

  Sending email is a "push" operation. The protocol used to transfer mail from a client to a mail server (and between mail servers) is SMTP (Simple Mail Transfer Protocol).

• $\text{m2}$: Downloading an email from a mailbox server to a mail client

  Retrieving email is a "pull" operation. Mail clients use protocols like POP (Post Office Protocol) or IMAP (Internet Message Access Protocol) to download messages from the mail server to the local client.

• $\text{m3}$: Checking email in a web browser

  When using a web browser to access email (webmail services like Gmail or Outlook.com), the browser communicates with the web server hosting the email service using HTTP (Hypertext Transfer Protocol).

Matching these with the options:

• $\text{m1} \rightarrow \text{SMTP}$
• $\text{m2} \rightarrow \text{POP}$
• $\text{m3} \rightarrow \text{HTTP}$

Therefore, the correct option is C.