mail.ericsontpa.com has no CNAME records.
Question and response
Question
dig mail.ericsontpa.com. NS
Answer
The response has no answer records.
Authority
ericsontpa.com. 300 SOA Erson-app-Srv2. hostmaster. 75 900 600 86400 300
Additional
. 0 OPT ; payload 1232, xrcode 0, version 0, flags 0