Source: https://help.ubuntu.com/community/Postfix/SPF#Verifying_It.27s_Working Postfix/SPF Contents Introduction SPF Package selection and installation Postfix Integration Enabling the Policy Service Reload Postfix Verifying It’s Working Introduction This guide explains how to install and integrate Sender Policy Framework (SPF)checking with Postfix. It applies all supported Ubuntu releases. SPF is an e-mail anti-forgery technology the enables domain owners to list, in the Domain Name…