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.

題解

「mailq」指令可以顯示準備寄出的信件清單。所以答案是選項D。