mx4.2gis.com has no CNAME records.
Question and response
Question
dig mx4.2gis.com. NS
Answer
The response has no answer records.
Authority
2gis.com. 1618 SOA ns.2gis.com. hostmaster.2gis.com. 2026030217 1200 300 2592000 1800
Additional
. 0 OPT ; payload 1232, xrcode 0, version 0, flags 0