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Email Fundamentals

Authentication

Authentication

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Authentication

Authentication

SPF, DKIM, and DMARC — how identity signals work together to protect delivery.

Reading time:: 8 min
Difficulty:: Intermediate
Estimated duration:: 8 min
Prerequisites:: Email Fundamentals
Last updated:: July 2026
Author:: Empire

Prerequisites

Email FundamentalsHow email moves across the internet — protocols, headers, and the path from sender to inbox.

Related Articles

SPFSender Policy Framework — authorize sending hosts and prevent spoofing.
DKIMDomainKeys Identified Mail — cryptographic signatures that prove message integrity.
DMARCDomain-based Message Authentication — policy, alignment, and reporting.

Related Problems

SPF ProblemsDiagnose SPF failures, softfails, include limits, and alignment issues.
DKIM ProblemsFix missing signatures, selector mismatches, and body hash failures.
DMARC ProblemsResolve alignment failures, policy enforcement blocks, and report gaps.

Recommended Tools

SendGridTransactional and marketing email platform with strong authentication tooling.
MailgunDeveloper-focused email API for transactional sending and inbound routing.
PostmarkReliable transactional email with strong deliverability defaults.

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NextSPFSender Policy Framework — authorize sending hosts and prevent spoofing.

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