serverbox-net.p30.spamhero.net has no MX records.
Question and response
Question
dig serverbox-net.p30.spamhero.net. MX
Answer
The response has no answer records.
Authority
serverbox-net.p30.spamhero.net. 86400 SOA ns.dnsbox.net. hostmaster.dnsbox.net. 2023062017 10000 3600 604800 172800
Additional
. 0 OPT ; payload 4096, xrcode 0, version 0, flags 0