Email was originally designed in an era when security was not a priority. As a result, the SMTP protocol has a major flaw: anyone can send an email pretending to be anyone else. To solve this, the internet engineering task force introduced three security protocols: SPF, DKIM, and DMARC.
1. SPF (Sender Policy Framework)
SPF is a simple DNS record that lists all the IP addresses authorized to send emails on behalf of your domain. When a mail server receives an email, it looks up the SPF record of the sender domain and checks if the sending IP address matches the list. If it doesn't, the email fails the SPF check.
2. DKIM (DomainKeys Identified Mail)
DKIM adds a cryptographic signature to the headers of your emails. The sender server signs the email using a private key, and the recipient server verifies the signature using the sender's public key published in their DNS record. This ensures that the email was not modified or tampered with in transit.
3. DMARC (Domain-based Message Authentication)
DMARC ties SPF and DKIM together. It tells recipient servers what to do if an email fails SPF or DKIM checks. You can configure DMARC to take three actions: None (monitor and report), Quarantine (send to spam folder), or Reject (block the email entirely). DMARC is the single most powerful tool to prevent domain hijacking.
"Implementing DMARC is no longer optional. Major email providers like Google and Yahoo now require it to ensure your emails reach the inbox."