mail3.ash206.ciberserver.com has no CNAME records.
Question and response
Question
dig mail3.ash206.ciberserver.com. NS
Answer
The response has no answer records.
Authority
ash206.ciberserver.com. 10800 SOA ns1.ciberserver.com. status.ciberconceito.com. 2018052004 3600 7200 1209600 86400
Additional
. 0 OPT ; payload 1232, xrcode 0, version 0, flags 0