_spf.mail.nic.md has no MX records.
Question and response
Question
dig _spf.mail.nic.md. MX
Answer
The response has no answer records.
Authority
nic.md. 1800 SOA annabel.ns.cloudflare.com. dns.cloudflare.com. 2397098573 10000 2400 604800 1800
Additional
. 0 OPT ; payload 1232, xrcode 0, version 0, flags 0