externalmx-useast.cuda-inc.com has no CNAME records.
Question and response
Question
dig externalmx-useast.cuda-inc.com. NS
Answer
The response has no answer records.
Authority
cuda-inc.com. 687 SOA ns1-06.azure-dns.com. root.cuda-inc.com.cuda-inc.com. 2041000954 7200 3600 86400 3600
Additional
. 0 OPT ; payload 1232, xrcode 0, version 0, flags 0