mail.xaas.systems has no CNAME records.
Question and response
Question
dig mail.xaas.systems. NS
Answer
The response has no answer records.
Authority
xaas.systems. 10800 SOA acns01.xaas.systems. support.anexia-it.com. 319 10000 7200 1209600 86400
Additional
. 0 OPT ; payload 1232, xrcode 0, version 0, flags 0