ALT3.ASPMX.L.GOOGLE.COM has no CNAME records.
Question and response
Question
dig ALT3.ASPMX.L.GOOGLE.COM. NS
Answer
The response has no answer records.
Authority
L.GOOGLE.COM. 25 SOA ns1.GOOGLE.COM. dns-admin.GOOGLE.COM. 873285235 900 900 1800 60
Additional
. 0 OPT ; payload 1232, xrcode 0, version 0, flags 0