_spf.co.ru has no MX records.
Question and response
Question
dig _spf.co.ru. MX
Answer
The response has no answer records.
Authority
co.ru. 3600 SOA ns1.gldn.net. dnsmaster.gldn.net. 2026011900 3600 600 3600000 3600
Additional
. 0 OPT ; payload 4096, xrcode 0, version 0, flags 0