smtp.exclaimer.com has no CNAME records.
Question and response
Question
dig smtp.exclaimer.com. NS
Answer
The response has no answer records.
Authority
exclaimer.com. 1800 SOA eva.ns.cloudflare.com. dns.cloudflare.com. 2397345830 10000 2400 604800 1800
Additional
. 0 OPT ; payload 1232, xrcode 0, version 0, flags 0