Impact on Inbox Placement with Google & Microsoft
- SPF + DKIM alone: 5-15% improvement in inbox placement
- SPF + DKIM + DMARC (p=none): 10-20% improvement (helps visibility but does not enforce protection)
SPF + DKIM + DMARC (p=quarantine or p=reject): 20-30% improvement (strongest impact, prevents spoofing)