Field guides

Deep guides to every layer of the stack.

Each guide takes one layer of the deliverability system and explains it the way a colleague would: what it is, how receivers actually use it, and what to do about it. Free to read, no signup. Start with the one closest to your situation, or learn the whole system first.

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Layer 5 · PlacementWhy are my emails going to spam?The honest answer, traced through the stack: reputation and records first, subject lines almost never.Layer 4 · ReputationGoogle Postmaster Tools explainedThe free window into Gmail's file on you: what every graph means and which number predicts trouble.Layer 2 · AuthenticationSPF, DKIM and DMARC in plain wordsThe three records that prove you are you. What each does, how they fit, and the order to set them up.Layer 2 · AuthenticationWhat is DMARC, really?From monitoring to enforcement without breaking your own mail. What p=reject stops, and what it does not.Layer 6 · ThreatEmail spoofing: how to stop itHow attackers send as your domain, how to tell it is happening, and the authentication that stops it.Layer 6 · ThreatBrand impersonation and lookalikesThe domains that copy yours one character off, the customers they fool, and how to catch them early.Layer 4 · ReputationDomain reputation and sender scoreThe receiver's memory, explained: what feeds your score, where to read it, and how long repair takes.Layer 1 · FoundationHow to read an email headerEvery delivered email carries its own diagnosis. What each header line means and how to trace a message.