mxbh.socketlabs.com has no CNAME records.
Question and response
Question
dig mxbh.socketlabs.com. NS
Answer
The response has no answer records.
Authority
socketlabs.com. 801 SOA ns-929.awsdns-52.net. dnsadmin.socketlabs.com. 2017110200 7200 900 1209600 86400
Additional
. 0 OPT ; payload 1232, xrcode 0, version 0, flags 0