_sv5.bitrix24.com has no CNAME records.
Question and response
Question
dig _sv5.bitrix24.com. NS
Answer
The response has no answer records.
Authority
bitrix24.com. 899 SOA ns.bitrixsoft.com. hostmaster.bitrixsoft.com. 2013102201 7200 900 1209600 86400
Additional
. 0 OPT ; payload 1232, xrcode 0, version 0, flags 0