The mailserver is currently called fred, while the primary MX record points to mailhost.example.org.



What must be done to direct example.org email towards fred?

A. Add an A record for mailhost to fred's IP address.
B. Add a CNAME record from mailhost to fred
C. Add another MX record pointing to fred's IP address.
D. Add a PTR record from mailhost to fred.

題解

若「fred」的IP為「216.158.76.21」,要達到題目描述的設定,DNS設定的方式應如下:

所以答案是選項A。