_spf3.sweb.ru has no MX records.
Question and response
Question
dig _spf3.sweb.ru. MX
Answer
The response has no answer records.
Authority
sweb.ru. 300 SOA ns1.sweb.ru. postmaster.sweb.ru. 2023050903 7200 3600 14400 300
Additional
. 0 OPT ; payload 4096, xrcode 0, version 0, flags 0