ip.unitedlayer.com has no MX records.
Question and response
Question
dig ip.unitedlayer.com. MX
Answer
The response has no answer records.
Authority
ip.unitedlayer.com. 10800 SOA ns1.unitedlayer.com. ed.unitedlayer.com. 2017062901 21600 3600 604800 10800
Additional
. 0 OPT ; payload 1232, xrcode 0, version 0, flags 0