mx2.smtp.goog has no CNAME records.
Question and response
Question
dig mx2.smtp.goog. NS
Answer
The response has no answer records.
Authority
smtp.goog. 300 SOA ns1.zdns.google. cloud-dns-hostmaster.google.com. 1 21600 3600 259200 300
Additional
. 0 OPT ; payload 1232, xrcode 0, version 0, flags 0