# Complaint rate: Definition and How It Works

Source: https://wraps.dev/glossary/complaint-rate

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Complaint rate is the share of delivered messages a recipient actively marked as spam, and AWS reviews an SES account at 0.1% and may pause sending at 0.5% — thresholds far tighter than the bounce-rate ones.

## It measures rejection, not a delivery problem

A bounce means the message failed to reach a mailbox. A complaint means it reached the mailbox, the recipient saw it, and actively clicked "report spam" or the equivalent. That makes complaint rate a stronger and more damaging signal than bounce rate for the same reason a customer complaint is worse for a business than an order that simply never arrived: it's evidence of active, specific rejection rather than a logistics failure.

## The visible number understates the real one

Complaint feedback only reaches the sender through mailbox providers that operate a feedback loop and report back — not every provider does, and not every recipient who is annoyed by a message bothers clicking report-spam versus simply deleting it or, worse, silently disengaging. What a sender can actually measure is a lower bound on how many recipients found the message unwanted, not the true figure.

## AWS's thresholds sit at a fraction of the bounce-rate ones

Where SES reviews bounce rate at roughly 5% and may pause at 10%, complaint rate is reviewed at 0.1% and may trigger a pause at 0.5% — fifty times tighter as a proportion. That gap reflects how much more weight a mailbox provider (and therefore AWS, whose own reputation with those providers depends on its senders' behavior) puts on an active complaint versus a failed delivery attempt.

## Suppression on complaint is not optional in practice

SES adds a complained-about address to the account-level suppression list the same way it does for a hard bounce, and sending to that address again is both against the point and, without an override, blocked by SES itself. The only real lever a sender has against complaint rate is upstream: better list acquisition, more relevant content, and an unsubscribe path recipients will actually use instead of the report-spam button.

## Why it matters

Complaint rate is the metric where the incentive structure most obviously rewards fixing the cause rather than the symptom — suppressing a complained-about address after the fact does nothing for the underlying reason recipients are complaining, which is almost always irrelevant content, unclear sender identity, or a broken unsubscribe path that pushes people toward reporting spam as the only visible way out.

## Common questions

### Why is the SES complaint-rate threshold so much lower than the bounce-rate one?

AWS reviews at 0.1% complaints against roughly 5% for bounces, because a complaint is direct evidence a real recipient saw the message and actively rejected it — a far stronger and more damaging signal to mailbox providers than a delivery failure.

### Does my measured complaint rate reflect every recipient who's annoyed?

No. It only counts complaints that a feedback-loop-participating mailbox provider actually reports back. Recipients who delete unwanted mail without clicking report-spam, or who are on a provider without a feedback loop, don't show up in the number at all.

### What actually lowers a persistently high complaint rate?

Upstream fixes: better list acquisition (see double opt-in), more relevant and expected content, and a working unsubscribe path recipients will actually use. Suppressing individual complained-about addresses after the fact doesn't touch the reason people are complaining.