What is a complaint rate?
Also called: spam rate, spam complaint rate
Complaint rate is the share of delivered messages that recipients mark as spam. Google asks senders to keep the rate shown in Postmaster Tools below 0.1% and never to reach 0.3%, and Yahoo sets the same 0.3% ceiling. It is the most direct signal mailbox providers have that mail is unwanted.
Providers measure complaints against mail that reached the inbox, so a small number of complaints on a modest send can push the rate over the line. A rate above 0.3% at Gmail can make a sender ineligible for mitigation support.
Complaints come from expectation more than content. People who did not ask for the mail, do not remember asking, or cannot find the unsubscribe link press the spam button instead.
Verification does not lower complaints directly, but it removes the addresses most likely to produce them: role addresses read by several people and recycled spam traps.
Example
Go deeper
Sources
By SimpleVerifier Team · Last reviewed 2026-10-13 · All 50 glossary terms