outbound.mailhop.org has no MX records.
Question and response
Question
dig outbound.mailhop.org. MX
Answer
The response has no answer records.
Authority
mailhop.org. 1800 SOA henry.ns.cloudflare.com. dns.cloudflare.com. 2397539225 10000 2400 604800 1800
Additional
. 0 OPT ; payload 1232, xrcode 0, version 0, flags 0