# Spam complaint rate: the number inbox providers watch

Spam complaint rate is the share of delivered email marked as spam. The Gmail and Yahoo thresholds, why it matters, and how Mimeo handles complaints.

**Definition:** Spam complaint rate is the share of delivered emails that recipients mark as spam. Gmail asks senders to keep it below 0.10% and never reach 0.30%.

## How it works

When someone presses "Report spam", their mailbox provider counts it against the sender. The rate is complaints divided by delivered messages. Three complaints on 1,000 delivered emails is 0.3%.

Each mailbox provider measures it on its own mail:

- **Gmail** shows a domain's spam rate in Postmaster Tools. Its guidelines say to keep it below 0.10% and avoid ever reaching 0.30%.
- **Yahoo** asks senders to stay below 0.3%, calculated on mail delivered to the inbox.

Some mailbox providers also send complaints back through feedback loops. Your sending provider receives them and passes them on to you.

## Why it matters

- **It drives spam filtering.** Gmail says a high spam rate leads to more of your mail landing in spam, and that improvements take time to show.
- **Complaints point at a cause.** People complain when they don't remember signing up, can't find the unsubscribe link, or hear from you too often.
- **The easy fix is a better button.** A reader who can unsubscribe in one tap doesn't need the spam button. That's why [List-Unsubscribe](https://mimeohq.com/glossary/list-unsubscribe) matters.

## How Mimeo handles it

Complaints arrive from Postmark or Resend by [webhook](https://mimeohq.com/docs/api/webhooks) and suppress the person immediately, with the reason recorded as a complaint. Nothing else goes to them. On Postmark a complaint is permanent: resubscribing someone in Mimeo can't clear it on Postmark's side ([Sending providers](https://mimeohq.com/docs/providers#how-the-providers-compare)).

Every email and broadcast report shows complaints next to delivered messages and bounces ([Reporting](https://mimeohq.com/docs/usage/reporting#delivery-is-confirmed-by-your-provider)), so you can see which send drew them. Mimeo can only count the complaints your provider reports back. Gmail's own figure for your domain is in Postmaster Tools. Every marketing email Mimeo sends also carries the one-click unsubscribe headers, so the inbox can show an unsubscribe button next to the spam button. See [Mimeo terms](https://mimeohq.com/docs/glossary#sending--deliverability) for complaints in Mimeo's own words.

## Sources

1. [Email sender guidelines](https://support.google.com/a/answer/81126), checked 2026-11-09
2. [Sender best practices](https://senders.yahooinc.com/best-practices/), checked 2026-11-09
3. [Webhooks](https://mimeohq.com/docs/api/webhooks), checked 2026-11-09
4. [Reporting](https://mimeohq.com/docs/usage/reporting), checked 2026-11-09
5. [Sending providers](https://mimeohq.com/docs/providers), checked 2026-11-04

---

This is the Markdown copy of https://mimeohq.com/glossary/spam-complaint-rate.