mx5.beget.com has no CNAME records.
Question and response
Question
dig mx5.beget.com. NS
Answer
The response has no answer records.
Authority
beget.com. 94 SOA ns1.beget.com. hostmaster.beget.com. 1771582073 300 600 86400 300
Additional
. 0 OPT ; payload 1232, xrcode 0, version 0, flags 0