Self-hosting your email? SPF, DKIM and DMARC decide your inbox rate

Short summary

A practical guide to self-hosting email deliverability covering SPF, DKIM, and DMARC configuration. SPF validates envelope sender IPs but breaks on forwarding; DKIM provides cryptographic signing that survives forwarding but breaks on content modification; DMARC enforces alignment between authenticated domains and the visible From address. The author also covers IP/domain reputation warming and a hard-won lesson about a single wrong character in a DKIM DNS record silently breaking signatures.

• •SPF, DKIM, and DMARC serve distinct, non-interchangeable roles in email authentication
• •DMARC alignment requires the passing domain to match the visible From address, not just a pass on SPF or DKIM
• •New IPs need gradual warm-up; domain reputation now matters more than IP reputation at Gmail and Outlook

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