mails1.ash2.ciberserver.com has no CNAME records.
Question and response
Question
dig mails1.ash2.ciberserver.com. NS
Answer
The response has no answer records.
Authority
ash2.ciberserver.com. 3278 SOA ns1.ciberserver.com. status.ciberconceito.com. 2018052000 3600 7200 1209600 86400
Additional
. 0 OPT ; payload 1232, xrcode 0, version 0, flags 0