xmbg9.mail.qq.com has no MX records.
Question and response
Question
dig xmbg9.mail.qq.com. MX
Answer
The response has no answer records.
Authority
mail.qq.com. 180 SOA qq.com. webmaster.qq.com. 1768972738 300 600 86400 180
Additional
. 0 OPT ; payload 4096, xrcode 0, version 0, flags 0