The most dangerous way to read Gmail's spam-rate chart is to assume that a lower number always means better inbox placement.

The chart measures user reports within a particular set of messages. If fewer people receive your mail in the inbox, there may also be fewer opportunities for them to report it there.

Understand the denominator

Google describes the metric as user-reported spam on DKIM-authenticated messages delivered to engaged recipients' inboxes. Messages recovered from spam through a Not spam action also contribute to the inbox-delivered population in its definition.

It is not the share of all messages Gmail put in spam. It is also not necessarily calculated from the same delivery total shown in your ESP.

For illustration, 10 complaints among 10,000 eligible inbox-delivered messages would equal 0.1%. This example explains the arithmetic. It does not let you recover the actual complaint count by multiplying the chart by your campaign's total recipients.

Use the thresholds as action points

Google recommends keeping spam rates below 0.1% and preventing them from reaching 0.3% or higher. Investigate before the higher threshold becomes a recurring feature of your sending.

If complaints rise, inspect the campaigns, audience sources and frequency changes around the affected date. Compare only complete days and align UTC reporting with your campaign calendar.

Investigate a sudden improvement

Imagine complaints fall after you stop a reactivation campaign. That gives you a specific change to evaluate. Now imagine complaints fall while reader activity drops and customers report spam placement. The same falling line would need a different investigation.

Use Feedback Loop data, where available, to narrow the affected program. Check clicks, replies and product outcomes without treating any single engagement measure as a placement test.

Separate recovery from support eligibility

Google says bulk senders restricted from mitigation because of high spam rates can become eligible again after seven consecutive days below 0.3%, subject to the other sender requirements. Zero complaints are not the stated threshold.

That condition is not a delivery guarantee. My recommendation is to keep the problematic audience paused until you understand why it generated complaints and can explain what will be different in the next send.

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