cdn-cname.pendo.io has no MX records.
Question and response
Question
dig 51.138.111.34.bc.googleusercontent.com. MX
Answer
The response has no answer records.
Authority
googleusercontent.com. 60 SOA ns1.google.com. dns-admin.google.com. 879543655 900 900 1800 60
Additional
. 0 OPT ; payload 512, xrcode 0, version 0, flags 0