---
title: "Spam complaint handling"
description: "Subscribe to available feedback loops, connect complaints to recipients safely, suppress them promptly, and monitor complaint rates by message stream."
canonical: https://specification.email/spec/deliverability/complaint-handling/
category: deliverability
status: required
sources:
  - title: "Complaint Feedback Loop operational recommendations"
    url: "https://www.m3aawg.org/sites/default/files/m3aawg-feedback-loop-best-common-practices-2018-07.pdf"
    publisher: "M3AAWG"
---

# Spam complaint handling

> Subscribe to available feedback loops, connect complaints to recipients safely, suppress them promptly, and monitor complaint rates by message stream.

## What it is

Some mailbox providers report when a recipient marks a message as spam. Complaint handling converts those reports into suppression and operational insight.

## Why it matters

Mailing a complainer again ignores an explicit negative signal and increases the chance that all mail from the stream is filtered.

## How to implement

Register authenticated domains for feedback loops, map reports to internal recipients without leaking personal data, suppress immediately, and segment metrics by source, campaign, and acquisition path.

## Common mistakes

- Treating complaints as a dashboard metric but not a suppression event.
- Logging entire message bodies unnecessarily.
- Averaging transactional and marketing streams together.

## Verification

Inject a synthetic complaint into the processing path and confirm the address cannot be queued again from any sending application.