mailer.helmes.com has no CNAME records.
Question and response
Question
dig mailer.helmes.com. NS
Answer
The response has no answer records.
Authority
helmes.com. 3600 SOA ns1.helmes.ee. hostmaster.helmes.ee. 2026021201 14400 3600 1209600 86400
Additional
. 0 OPT ; payload 1232, xrcode 0, version 0, flags 0