mailus.ingenico.com has no MX records.
Question and response
Question
dig mailus.ingenico.com. MX
Answer
The response has no answer records.
Authority
ingenico.com. 60 SOA dns1.p05.nsone.net. hostmaster.nsone.net. 1655811587 7200 1800 2419200 60
Additional
. 0 OPT ; payload 1232, xrcode 0, version 0, flags 0