Email deliverability checks, explained

Plain-language explanations and fixes for every check we run when scoring your email.

Authentication & Alignment

SPF authentication SPF record quality DKIM signature DMARC policy published DMARC alignment (pass)

Sending Infrastructure

Reverse DNS (PTR) + FCrDNS HELO/PTR hostname quality TLS in transit Sender domain has MX Received-chain sanity

Reputation & Blocklists

Sending IP blocklist (Spamhaus ZEN)Sending IP corroborating blocklists Sender domain blocklist (Spamhaus DBL)Body-link domain reputation (SURBL/URIBL)Sender domain age

Content & Structure

SpamAssassin content score Plain-text alternative present Text-to-image balance Link safety & quality Subject & body hygiene Obfuscation / evasion

Compliance & List Hygiene

List-Unsubscribe header One-click unsubscribe (RFC 8058)Unsubscribe link in body Physical postal address RFC 5322 header completeness

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