# Email authentication knowledge base

> Understand SPF, DKIM, DMARC and email headers. Follow practical guides from an authentication result to your next test.

By [CheckDMARC](https://checkdmarc.mx/). Published: 2026-11-06. Updated: 2026-11-06.

[Start with the testing walkthrough](https://checkdmarc.mx/how-it-works/index.md)

[Compare SPF, DKIM and DMARC](https://checkdmarc.mx/spf-dkim-dmarc/index.md)

- [SPF: check which servers can send for your domain](https://checkdmarc.mx/learn/spf/index.md): Read an SPF result, identify the envelope sender and investigate a failure without guessing which DNS record to change. Reviewed 2026-11-06.

- [DKIM: understand the signature on your email](https://checkdmarc.mx/learn/dkim/index.md): Find the DKIM signing domain and selector, interpret a reported signature result and check whether it helps your domain pass DMARC. Reviewed 2026-11-06.

- [DMARC: connect authentication to your From domain](https://checkdmarc.mx/learn/dmarc/index.md): Understand DMARC alignment, the difference between a message result and a published policy, and how to investigate your report. Reviewed 2026-11-06.

- [Email authentication headers: what to copy and read](https://checkdmarc.mx/learn/email-authentication-headers/index.md): Locate original message headers, find Authentication-Results and keep the evidence needed to understand an SPF, DKIM or DMARC report. Reviewed 2026-11-06.

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