Which protocol is used to send email?

A.
File Transfer Protocol (FTP).

B.
Post Office Protocol (POP).

C.
Network File System (NFS).

D.
Simple Mail Transfer Protocol (SMTP).

Explanation:
In e-mail clients SMTP works as a message transfer agent and moves the message from the user’s computer
to the mail server when the user sends the e-mail message.
Incorrect Answers:
A: FTP is a network application that supports an exchange of files between computers.
B: The Post Office Protocol (POP) is an application-layer Internet standard protocol used by local e-mail clients
to retrieve, not to send, e-mail from a remote server over a TCP/IP connection.
C: The Network File System (NFS) is a client/server application that lets a computer user view and optionally
store and update file on a remote computer as though they were on the user’s own computer.
Harris, Shon, All In One CISSP Exam Guide, 6th Edition, McGraw-Hill, New York, 2013, p. 599