Spam complaint

The report-spam button is the loudest signal in email. What it triggers, and what it costs.

A spam complaint is generated when a recipient clicks the report-spam button in their mail client. The mailbox provider counts the complaint against your sending reputation and, if a feedback loop exists, tells you it happened.

Why it matters

Complaints are the strongest negative signal in email, weighted far above an unsubscribe: a human told their provider that your mail is abuse. Gmail's bulk-sender rules make the budget explicit: a spam rate of 0.3% in Postmaster Tools is the danger line past which bulk mail gets junked, and Google's guidance is to stay under 0.1%. That is three complaints per thousand messages at the line, one per thousand to be safe. It is a small budget, and reputations recover slowly once it is spent.

In practice

The complaining address must never be mailed again; treat the complaint as an unsubscribe delivered in the harshest available way. Beyond suppression, complaint patterns are diagnostic. Spikes cluster around cold or aged lists, sudden jumps in frequency, subject lines that overpromise, and audiences that never opted in cleanly, which is the problem double opt-in exists to prevent. Watching complaint rate per campaign and per stream tells you which of your mail is earning its place in the inbox and which is renting it.

How Email Fast handles it

Complaints reaching Email Fast through provider feedback loops trigger instant suppression of the complainer: one complaint, zero further sends to that address, on the first report. Feedback-loop enrollment is tied to live delivery, so this lane arms with sending at launch; the suppression machinery it feeds is the same one gate every send already passes through.