c2.bitrix24.com has no CNAME records.
Question and response
Question
dig c2.bitrix24.com. NS
Answer
The response has no answer records.
Authority
bitrix24.com. 668 SOA ns.bitrixsoft.com. hostmaster.bitrixsoft.com. 2013102201 7200 900 1209600 86400
Additional
. 0 OPT ; payload 1232, xrcode 0, version 0, flags 0