Question and response
Question
dig dnsv4.com. MX
Answer
dnsv4.com. 600 MX 5 mxbiz1.qq.com.
Authority
dnsv4.com. 86400 NS ns4.dnsv4.net.
dnsv4.com. 86400 NS ns3.dnsv4.com.
Additional
. 0 OPT ; payload 1280, xrcode 0, version 0, flags 0