How to Set Up SPF, DKIM, and DMARC to Fix Email Deliverability Issues

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Email authentication relies on three DNS-based mechanisms — SPF, DKIM, and DMARC — that together verify sender identity and protect domains from spoofing. SPF specifies which servers are authorised to send mail for a domain, DKIM cryptographically signs messages to confirm they were not tampered with, and DMARC sets the policy for handling failures while generating reports. Common setup mistakes include publishing duplicate SPF records, proxying DKIM CNAME entries through Cloudflare, and jumping straight to a strict DMARC rejection policy before monitoring legitimate mail flows. Experts recommend starting DMARC in monitoring mode (p=none) for a few weeks to identify all sending sources before escalating to quarantine and then reject. Since 2024, both Gmail and Yahoo require a valid DMARC record for bulk senders, making proper configuration essential for inbox delivery.

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