mail.virtualxs.com has no CNAME records.
Question and response
Question
dig mail.virtualxs.com. NS
Answer
The response has no answer records.
Authority
virtualxs.com. 3035 SOA ns1.virtualxs.com. hostmaster.virtualxs.com. 2023091304 7200 7200 604800 86400
Additional
. 0 OPT ; payload 1232, xrcode 0, version 0, flags 0