Spam complaint
Definition
A spam complaint is a recipient clicking "report as spam" in their inbox. The complaint rate is complaints divided by sends; it is the lowest and most serious deliverability threshold.
How it is computed, where to read it
A complaint is often a consent problem (the person does not remember signing up) or a pressure problem (too many sends).
Klaviyo records complaints in the Marked Email as Spam metric and removes the profile from sends.
The account average can hide a struggling provider: an account at 0.15% on average can be blocked at Gmail. KlaviBoard alerts on the account above 0.1% and, per provider, above 0.25%.
The threshold
Above 0.1% on the account, or 0.25% at a single provider: KlaviBoard alert rules. Gmail asks you to stay under 0.1%.