ip.serverbox.net has no MX records.
Question and response
Question
dig ip.serverbox.net. MX
Answer
The response has no answer records.
Authority
ip.serverbox.net. 900 SOA ns.dnsbox.net. hostmaster.dnsbox.net. 2026022111 86400 7200 3600000 900
Additional
. 0 OPT ; payload 4096, xrcode 0, version 0, flags 0