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Email Deliverability Standards

Technical standards for email deliverability and authentication

emaildeliverabilitytechnicalauthentication
Version 1.0.0Updated Dec 29, 2025
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Checks

SPF record exists

Sender Policy Framework configured

Based on SPF (RFC 7208)

critical

DKIM signature present

DomainKeys Identified Mail configured

Based on DKIM (RFC 6376)

critical

DMARC record exists

Domain-based Message Auth configured

Based on DMARC (RFC 7489)

critical

List-Unsubscribe header

One-click unsubscribe support

Based on RFC 2369

major

Valid From address

From address matches sending domain

Based on RFC 5322

critical

Text-to-image ratio 60:40

Avoid image-only emails

Based on Best Practice

major

No excessive spam words

Limit spam trigger words

Based on Best Practice

major

Proper Message-ID

Unique message identifier

Based on RFC 5322

minor