структура політики фільтрації відправників(An extension of the SMTP protocol that prevents spammers from forging the From: fields in e-mail messages by verifying that the IP address in the SMTP Received: header is authorized to send e-mail for the sender's domain)
Sender Policy Framework(An extension of the SMTP protocol that prevents spammers from forging the From: fields in e-mail messages by verifying that the IP address in the SMTP Received: header is authorized to send e-mail for the sender's domain)
