mx20.glide.email has no CNAME records.
Question and response
Question
dig mx20.glide.email. NS
Answer
The response has no answer records.
Authority
glide.email. 3600 SOA ns0.server.fido.net. hostmaster.glide.email. 2025111500 10800 3600 604800 3600
Additional
. 0 OPT ; payload 1232, xrcode 0, version 0, flags 0