Consider different activities related to email:
m1: Send an email from a mail client to a mail server m2: Download an email from mailbox server to a mail client m3: Checking email in a web browser
Which is the application level protocol used in each activity?
(A) m1: HTTP m2: SMTP m3: POP
(B) m1: SMTP m2: FTP m3: HTTP
(C) m1: SMTP m2: POP m3: HTTP
(D) m1: POP m2: SMTP m3: IMAP
Explanation: Simple Mail Transfer Protocol (SMTP) is typically used by user clients for sending mails.
Post Office Protocol (POP) is used by clients for receiving mails.
Checking mails in web browser is a simple HTTP process.
Option (C) is correct.