mailboxes.regionalnet.org has no CNAME records.
Question and response
Question
dig mailboxes.regionalnet.org. NS
Answer
The response has no answer records.
Authority
regionalnet.org. 10709 SOA ns1.netprotect.ro. alex.regionalnet.org. 2021100101 28800 7200 10800 10800
Additional
. 0 OPT ; payload 1232, xrcode 0, version 0, flags 0