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Foundations

Email Fundamentals

Authentication

Authentication

Deliverability

Deliverability

Infrastructure

Infrastructure

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Authentication
SPF

SPF

Sender Policy Framework — authorize sending hosts and prevent spoofing.

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

Prerequisites

AuthenticationSPF, DKIM, and DMARC — how identity signals work together to protect delivery.
Email FundamentalsHow email moves across the internet — protocols, headers, and the path from sender to inbox.

Related Articles

DKIMDomainKeys Identified Mail — cryptographic signatures that prove message integrity.
DMARCDomain-based Message Authentication — policy, alignment, and reporting.
DeliverabilityWhy messages land in spam, promotions, or the inbox — and how providers decide.

Related Problems

SPF ProblemsDiagnose SPF failures, softfails, include limits, and alignment issues.
Gmail SpamDiagnose why Gmail is filtering messages to spam or promotions.

Recommended Tools

SendGridTransactional and marketing email platform with strong authentication tooling.
MailgunDeveloper-focused email API for transactional sending and inbound routing.
Amazon SESHigh-scale cloud email sending with fine-grained infrastructure control.

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NextDKIMDomainKeys Identified Mail — cryptographic signatures that prove message integrity.

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