What is the purpose of the command mailq?
A.
It fetches new emails from a remote server using POP3 or IMAP.
B.
It is a multi-user mailing list manager.
C.
It is a proprietary tool contained only in the qmail MTA.
D.
It queries the mail queue of the local MTA.
E.
It is a command-line based tool for reading and writing emails.