standard.mask.ad has no MX records.
Question and response
Question
dig standard.mask.ad. MX
Answer
The response has no answer records.
Authority
mask.ad. 1800 SOA ben.ns.cloudflare.com. dns.cloudflare.com. 2394529499 10000 2400 604800 1800
Additional
. 0 OPT ; payload 1232, xrcode 0, version 0, flags 0