ftn.rocks has no MX records.
Question and response
Question
dig ftn.rocks. MX
Answer
The response has no answer records.
Authority
ftn.rocks. 86400 SOA pdns104.ultradns.com. tldadmin.iristel.com. 2018032704 86400 86400 86400 86400
Additional
. 0 OPT ; payload 4096, xrcode 0, version 0, flags 0