mail.mxthunder.net has no MX records.
Question and response
Question
dig mail.mxthunder.net. MX
Answer
The response has no answer records.
Authority
mxthunder.net. 172800 SOA ns.dnsbox.net. hostmaster.dnsbox.net. 2026012006 10000 3600 604800 172800
Additional
. 0 OPT ; payload 4096, xrcode 0, version 0, flags 0