tugu.as23951.com has no MX records.
Question and response
Question
dig tugu.as23951.com. MX
Answer
The response has no answer records.
Authority
as23951.com. 1800 SOA deb.ns.cloudflare.com. dns.cloudflare.com. 2394319099 10000 2400 604800 1800
Additional
. 0 OPT ; payload 1232, xrcode 0, version 0, flags 0