ALT2.ASPMX.L.GOOGLE.com has no CNAME records.
Question and response
Question
dig ALT2.ASPMX.L.GOOGLE.com. NS
Answer
The response has no answer records.
Authority
l.google.com. 47 SOA ns1.google.com. dns-admin.google.com. 873285235 900 900 1800 60
Additional
. 0 OPT ; payload 1232, xrcode 0, version 0, flags 0