Metrics
Complaint rate
The percentage of recipients who mark your email as spam. Should be kept below 0.1%.
Definition
Complaint rate is the percentage of recipients who mark your email as spam. It's calculated as (spam complaints ÷ emails delivered) × 100. Major mailbox providers like Gmail and Yahoo consider a complaint rate above 0.1% (1 in 1,000) as problematic. Rates above 0.3% can trigger immediate deliverability issues. Complaint rates are tracked through feedback loops (FBLs) from ISPs.
Examples
- 10,000 emails sent, 5 complaints = 0.05% (healthy)
- 10,000 emails sent, 50 complaints = 0.5% (problematic)
Need help with email verification?
Check addresses through the API or clean a whole list from a CSV upload.
100 free verifications. No credit card required.