ns2.sqr.domains has no MX records.
Question and response
Question
dig ns2.sqr.domains. MX
Answer
The response has no answer records.
Authority
sqr.domains. 300 SOA ns1.cyso.nl. dnsadmin.cysonet.com. 1772668800 16384 2048 1048576 300
Additional
. 0 OPT ; payload 4096, xrcode 0, version 0, flags 0