GATE CS 2019 Q16 — Application Layer Protocols: DNS, SMTP, HTTP, FTP, Email

To understand which protocols are used for sending and retrieving emails, let's analyze their functions:

• SMTP (Simple Mail Transfer Protocol): Used to send emails from a client to a mail server, and to transfer emails between mail servers.
• POP3 (Post Office Protocol version 3) and IMAP (Internet Message Access Protocol): Used by a client to retrieve emails from a mail server.
• MIME (Multipurpose Internet Mail Extensions): An extension to the email protocol that allows sending non-ASCII data (like images, audio, video, etc.) but is not a transfer or retrieval protocol itself.

Therefore, to send and retrieve emails in that order, the correct pair is SMTP and POP3 (or IMAP).

Thus, Option B is the correct answer.