cloud-mailer.bitrix.info has no CNAME records.
Question and response
Question
dig cloud-mailer.bitrix.info. NS
Answer
The response has no answer records.
Authority
bitrix.info. 900 SOA ns-1979.awsdns-55.co.uk. hostmaster.bitrixsoft.com. 2 7200 900 1209600 86400
Additional
. 0 OPT ; payload 1232, xrcode 0, version 0, flags 0