smtp.covad.com has no CNAME records.
Question and response
Question
dig smtp.covad.com. NS
Answer
The response has no answer records.
Authority
covad.com. 300 SOA ns1.gtt.net. dnsadmin.gtt.net. 2026030501 14400 600 2718281828 300
Additional
. 0 OPT ; payload 1232, xrcode 0, version 0, flags 0