b.ns.qst.global has no MX records.
Question and response
Question
dig b.ns.qst.global. MX
Answer
The response has no answer records.
Authority
qst.global. 2560 SOA a.ns.qst.global. hostmaster.qst.global. 1772677116 16384 2048 1048576 2560
Additional
The response has no additional records.