mail.broadcloudpbx.com has no CNAME records.
Question and response
Question
dig mail.broadcloudpbx.com. NS
Answer
The response has no answer records.
Authority
broadcloudpbx.com. 120 SOA hns001.sjc03.webex.com. aquebedeaux.broadsoft.com. 2013025685 10800 1800 2419200 120
Additional
. 0 OPT ; payload 1232, xrcode 0, version 0, flags 0