mailfilter.hostsailor.net has no CNAME records.
Question and response
Question
dig mailfilter.hostsailor.net. NS
Answer
The response has no answer records.
Authority
hostsailor.net. 1800 SOA chuck.ns.cloudflare.com. dns.cloudflare.com. 2395286744 10000 2400 604800 1800
Additional
. 0 OPT ; payload 1232, xrcode 0, version 0, flags 0