mail.acserviceall.com has no CNAME records.
Question and response
Question
dig mail.acserviceall.com. NS
Answer
The response has no answer records.
Authority
acserviceall.com. 5926 SOA ns21.ecomsiam.com. technical.ecomsiam.com. 2026012503 3600 1800 1209600 86400
Additional
. 0 OPT ; payload 1232, xrcode 0, version 0, flags 0