Metrics
Updated
Spam complaint rate
Definition
Spam complaint rate is the percentage of delivered emails that recipients reported as spam. Gmail and Yahoo require bulk senders to stay below 0.3% and recommend staying below 0.1%.
How it works
Complaint rate = spam reports / delivered emails x 100. It is measured against delivered mail, because only delivered mail can be reported.
Senders learn about complaints through feedback loops (FBLs). Yahoo, Microsoft and other providers send a report in Abuse Reporting Format (RFC 5965) for each complaint. Gmail does not send per-message reports to senders and instead shows an aggregate spam rate in Google Postmaster Tools.
Because some providers report nothing, the complaint rate your ESP shows is a lower bound. Postmaster Tools is the reference for Gmail.
Example
0.12% is above the recommended 0.1%. Narrow the audience before the next send.
Why it matters
Complaints are the strongest negative signal mailbox providers use. Gmail's sender guidelines say bulk senders must keep the spam rate in Postmaster Tools below 0.3%, and staying under 0.1% is the recommendation.
People click Report spam when they do not remember signing up, cannot find the unsubscribe link, or get more mail than expected.
Benchmarks
- Aim for under 0.1% on every send. Treat 0.3% as a hard ceiling, not a target.
- Offer one-click unsubscribe and a visible link in the footer. A hidden unsubscribe becomes a spam report.
- Only email people who opted in, and send what they signed up for at the frequency they expect.
- Suppress every complainer permanently.
- Make the sender name and subject recognizable so subscribers know who you are.
| Complaint rate | Status |
|---|---|
| Under 0.1% | Healthy, recommended by Gmail and Yahoo |
| 0.1% to 0.3% | At risk, tighten targeting now |
| 0.3% or higher | Above the 2024 bulk sender limit, expect filtering |
How Lumail handles spam complaint rate
Lumail uses feedback-loop complaints as a share of delivered mail across consecutive windows with enough volume. Around 0.08% raises a warning and 0.1% an error, so you act before reaching the provider limits.
Every complaining address is suppressed automatically, and Lumail adds one-click unsubscribe headers to every campaign and workflow email.
Check a real message with the free mail tester or the spam tester.
Frequently asked questions
What is a good spam complaint rate?
Below 0.1%, meaning fewer than 1 complaint per 1,000 delivered emails. Gmail and Yahoo require bulk senders to stay below 0.3%.
Why does my ESP show fewer complaints than Postmaster Tools?
Gmail does not send per-message complaint reports to senders. ESP numbers come from providers with feedback loops, so Postmaster Tools is the only source for Gmail's spam rate.
How do I lower my complaint rate quickly?
Stop sending to unengaged and unconfirmed contacts, make unsubscribe one click, and send only what people signed up for. Complaints usually drop within a few sends.
Related terms, tools and docs
- List managementOne-click unsubscribeOne-click unsubscribe is a standard (RFC 8058) that lets mail clients unsubscribe a recipient with a single HTTPS POST, without opening a web page.
- DeliverabilitySender reputationSender reputation is the trust score mailbox providers assign to your sending domain and IP addresses, based on how recipients and their systems react to your mail.
- List managementDouble opt-inDouble opt-in (confirmed opt-in) is a signup process where a new subscriber must click a link in a confirmation email before they are added to the list.
- List managementList hygieneList hygiene is the routine of removing or suppressing email addresses that hurt deliverability: hard bounces, spam complainers, long-inactive subscribers, invalid addresses and likely spam traps..
- Free toolFree spam testerCheck an email for the patterns that push mail to spam.
- Free toolFree mail testerSend a real email and get an SPF, DKIM, DMARC and content report.
- DocsHow to lower complaint rateStop mailing people who report spam.
- DocsSender healthHow Lumail measures sending health and authentication.
- DocsAutomatic list cleanupUnsubscribe people inactive for 30, 90 or 180 days.
Browse every definition in the email marketing glossary.
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