SPF (Sender Policy Framework) is a system that identifies to mail servers what hosts are allowed to send email for a given domain. Setting up SPF helps to prevent your email from being classified as spam. DKIM (DomainKeys Identified Mail) is a system that lets your official mail servers add a signature to headers of outgoing email and identifies your domain’s public key so other mail servers can verify the signature. As with SPF, DKIM helps keep your mail from being considered spam. It also lets mail servers detect when your mail has been tampered with in transit. The instructions for setting up DNS for SPF and DKIM are generic. The instructions for configuring the SPF policy agent and OpenDKIM into Postfix should work on any distribution after making respective code adjustments for the package tool and to identify the exact path to OpenDKIM’s socket file in Postfix. The steps required in this guide require root privileges. Be sure to run the steps below as ...