mx1.beget.com has no CNAME records.
Question and response
Question
dig mx1.beget.com. NS
Answer
The response has no answer records.
Authority
beget.com. 240 SOA ns1.beget.com. hostmaster.beget.com. 1771582073 300 600 86400 300
Additional
. 0 OPT ; payload 1232, xrcode 0, version 0, flags 0