mail.alt255.net has no MX records.
Question and response
Question
dig mail.alt255.net. MX
Answer
The response has no answer records.
Authority
alt255.net. 1800 SOA gina.ns.cloudflare.com. dns.cloudflare.com. 2397930542 10000 2400 604800 1800
Additional
. 0 OPT ; payload 1232, xrcode 0, version 0, flags 0