Spam complaint rate
The complaint rate is the share of your delivered messages that readers marked as spam, measured per mailbox provider rather than across your whole audience. It is the number providers watch most closely, because it is the most direct statement their own users can make about your mail. A rising rate costs you the inbox long before anyone tells you.
At a glance
- Category
- Deliverability
- Measured as
- Complaints divided by delivered messages, per provider
- Google's threshold
- Below 0.3%, per its sender guidelines
- Denominator
- Messages that provider accepted, not your whole send
- Worst driver
- Mailing people who did not ask, or have not heard from you in months
- Visible through
- Feedback loops, and provider postmaster tools
How it works
Every time a reader presses the spam button, their mailbox provider records it. The rate is that count divided by the messages that provider accepted from you, over a window it chooses. Because the denominator is per provider, one provider's audience can be in serious trouble while your overall average looks healthy, which is why the aggregate number is close to useless on its own. Some providers report the rate back through postmaster tools; others only reveal it through its consequences.
Why it matters
Google's sender guidelines ask bulk senders to keep the rate below 0.3% and warn that reaching that level risks filtering. That is a threshold for trouble, not a target: mail people actually asked for usually sits an order of magnitude below them. Watching the rate per provider is what turns a slow decline into something you notice in week one rather than in the quarter's numbers. The threshold is also a floor for action rather than a line you may sit on, because a provider that is close to intervening is already filtering some of your mail.
Example
A team's overall complaint rate reads 0.08% and nobody worries. Split by provider, one large consumer provider is at 0.35% while every other is near zero. The difference turns out to be a segment imported eighteen months earlier, almost all of it addresses at that one provider. They stop mailing that segment, the provider's rate falls back over a month, and placement recovers without anything else changing.
Common mistakes
- 01Watching one blended number, which averages a serious problem at one provider into a comfortable total.
- 02Making the unsubscribe hard to find, which converts departures into complaints and makes the rate worse rather than the list larger.
- 03Reacting to a spike by sending more, which supplies the provider with more of the evidence that caused the problem.
- 04Treating a threshold as a target, when a well-consented list normally sits far below the level at which anybody intervenes.
In Rasket
The metrics endpoint reports a complaint rate alongside deliveries and bounces, so the number can be watched from your own dashboards. Metrics reference
Related terms
Frequently asked questions
What complaint rate is acceptable?
Google's sender guidelines name 0.3% as the level at which bulk senders risk filtering, and ask senders to stay below it. Lists built from genuine consent usually run far lower than that.
Why does my rate differ so much between providers?
Because the audience differs and so does the button. Providers count and weight complaints differently, and a segment concentrated at one provider will show up there and nowhere else.
Can I reduce the rate without shrinking the list?
Sometimes, by making the unsubscribe control obvious and by mailing less often. Beyond that, the reliable lever is not sending to people who do not want it, which does shrink the list.
Sources
- Email sender guidelines: spam rate — Google
Last updated 16 September 2026.
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