smtp.webmercs.com has no CNAME records.
Question and response
Question
dig smtp.webmercs.com. NS
Answer
The response has no answer records.
Authority
webmercs.com. 240 SOA ns-cloud-c1.googledomains.com. cloud-dns-hostmaster.google.com. 21 21600 3600 1209600 300
Additional
. 0 OPT ; payload 1232, xrcode 0, version 0, flags 0