mail.dc.volia.com has no CNAME records.
Question and response
Question
dig mail.dc.volia.com. NS
Answer
The response has no answer records.
Authority
dc.volia.com. 1809 SOA ns0.dc.volia.com. hostmaster.dc.volia.com. 2025052900 14400 3600 604800 3600
Additional
. 0 OPT ; payload 1232, xrcode 0, version 0, flags 0