Email Deliverability Knowledge Base

Plain-language, MTA-agnostic reference on getting email delivered — authentication, provider requirements, list hygiene, compliance, and ESP operations.

Tools

Check any sending domain's SPF, DKIM, DMARC, MX and blocklist status in a few seconds, free.

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Learn

Foundations
How delivery actually works, and what mailbox providers measure.
Mailbox Providers
What Gmail, Yahoo, Microsoft and Apple require of senders who send in volume.
Authentication
SPF, DKIM, DMARC, ARC and BIMI, record by record.

Browse every topic, with its article count

Services

Deliverability audit — USD 1,500, a fixed scope for a fixed price.

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