NS4.FASTTRACKDNS.com has no MX records.
Question and response
Question
dig NS4.FASTTRACKDNS.com. MX
Answer
The response has no answer records.
Authority
FASTTRACKDNS.com. 38400 SOA NS1.101DOMAIN.com. ADMIN.FASTTRACKDNS.com. 2015011505 10800 3600 604800 38400
Additional
. 0 OPT ; payload 1232, xrcode 0, version 0, flags 0