mailer.whmpanels.com has no MX records.
Question and response
Question
dig mailer.whmpanels.com. MX
Answer
The response has no answer records.
Authority
mailer.whmpanels.com. 30 SOA ns1.romarg.com. hostmaster.romarg.com. 2023112800 1200 1200 1209600 3600
Additional
. 0 OPT ; payload 1232, xrcode 0, version 0, flags 0