ns6604.hostgator.com has no MX records.
Question and response
Question
dig ns6604.hostgator.com. MX
Answer
The response has no answer records.
Authority
hostgator.com. 1800 SOA cody.ns.cloudflare.com. dns.cloudflare.com. 2397870024 10000 2400 604800 1800
Additional
. 0 OPT ; payload 1232, xrcode 0, version 0, flags 0