Sender Policy Framework - Wikipedia
https://en.wikipedia.org/wiki/Sender_Policy_Framework
Sender Policy Framework (SPF) is an email authentication method designed to detect forging sender addresses during the delivery of the email.
SPF record - Yandex.Connect. Help
https://yandex.com/support/connect/dns/spf.html
The SPF record helps reduce the risk of email sent from an address on your domain being put in To configure the SPF record, create a TXT record with a list of servers that send email from your domain.