mail1.eskerondemand.com has no MX records.
Question and response
Question
dig mail1.eskerondemand.com. MX
Answer
The response has no answer records.
Authority
eskerondemand.com. 3600 SOA ns1.esker.com. freodoperation.esker.fr. 2026013001 1800 900 604800 3600
Additional
. 0 OPT ; payload 4000, xrcode 0, version 0, flags 0