ns2.qq.com has no MX records.
Question and response
Question
dig ns2.qq.com. MX
Answer
The response has no answer records.
Authority
qq.com. 180 SOA ns1.qq.com. webmaster.qq.com. 1768982963 300 600 86400 180
Additional
. 0 OPT ; payload 4096, xrcode 0, version 0, flags 0