sl2.sedo.com has no MX records.
Question and response
Question
dig sl2.sedo.com. MX
Answer
The response has no answer records.
Authority
sedo.com. 1800 SOA emily.ns.cloudflare.com. dns.cloudflare.com. 2395600958 10000 2400 604800 1800
Additional
. 0 OPT ; payload 1232, xrcode 0, version 0, flags 0