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sender reputation

How sender-reputation scoring actually works

Reputation is not a single number. It is a bundle of signals a mailbox provider watches per domain and per IP — and crossing one threshold can silently move you to spam.

2026-06-08 · 7 min read

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Ask five people what "sender reputation" means and you get five different answers. Underneath, mailbox providers like Gmail expose (via Postmaster Tools) a specific set of signals, and it is worth knowing what each one actually measures.

The signals that matter

  • Spam rate — the share of your delivered mail users mark as spam. Gmail treats anything sustained above roughly 0.3% as a warning sign and 0.1% as the safe ceiling to stay under.
  • IP reputation and domain reputation — tracked separately; a good domain on a bad shared IP (or vice versa) still gets flagged.
  • Authentication rate — the share of your mail that passes SPF/DKIM/DMARC alignment cleanly. See SPF, DKIM & DMARC explained if any of that is unfamiliar.
  • Delivery errors — the rate of temporary and permanent failures, which spikes when you keep mailing bounced or invalid addresses.
  • Feedback loop / user-reported spam — direct complaint signals from mailbox providers that supply them.

Why one bad batch can sink a whole domain

These signals are aggregated per sending domain (and per IP) over a rolling window, not per campaign. Send one poorly targeted batch that spikes complaints, and the resulting reputation dip applies to every message that domain sends afterward — including the good ones. That is why "just send more carefully next time" does not undo the damage; the domain needs time, or a fresh one, to recover.

Why a circuit-breaker beats a dashboard

Postmaster Tools shows you the damage after receivers have already reacted — usually with a day or more of lag. By the time a human notices the spam-rate graph ticking up, the domain has often already been sending degraded mail for hours. A reputation circuit-breaker watches the same signals continuously and pauses the domain automatically the moment it drifts past a safe threshold, instead of waiting for someone to check a dashboard.

For the full authentication and warmup picture, see the deliverability checklist and what a warmed sender pool is. Or check your own domain right now with the free SPF checker and blacklist checker.

Let CogniLead run deliverability

Warmed pools, a reputation circuit-breaker, suppression on every send — per send, via API or MCP.

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2026-06-26 · 6 min read

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SPF, DKIM, and DMARC: the setup that lands in the inbox

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2026-06-20 · 6 min read

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You can send transactional email from your app in five minutes — but try cold outbound and you will get banned. Here is the layer built for it.

How sender-reputation scoring works — Postmaster signals