dns4.cernet.net has no MX records.
Question and response
Question
dig dns4.cernet.net. MX
Answer
The response has no answer records.
Authority
cernet.net. 600 SOA ns2.net.edu.cn. hostmaster.dns.edu.cn. 2002021861 7200 1800 604800 600
Additional
. 0 OPT ; payload 1232, xrcode 0, version 0, flags 0