ns1.dns.net.kh has no MX records.
Question and response
Question
dig ns1.dns.net.kh. MX
Answer
The response has no answer records.
Authority
dns.net.kh. 10800 SOA ns.camnet.com.kh. ict_camservice\@camnet.com.kh. 2021021113 28800 7200 1209600 86400
Additional
. 0 OPT ; payload 1232, xrcode 0, version 0, flags 0