Email Marketing & Klaviyo

Spam Complaint Rate

The percentage of recipients who mark your email as spam. Should remain below 0.1%.

1 min readLast updated Apr 2026

The percentage of recipients who mark your email as spam. Should remain below 0.1%.

Why It Matters

Spam complaints are the most damaging engagement signal. ISPs heavily weight complaints—even 0.1% (1 per 1,000) can trigger deliverability issues. Above 0.3% may result in domain blacklisting. Unlike unsubscribes (neutral), spam complaints actively harm your reputation.

Practical Example

Scenario

A supplements brand sends 80,000 emails and receives 120 spam complaints.

Calculation

120 ÷ 80,000 × 100 = 0.15% spam complaint rate

Result

At 0.15%, they're above the 0.1% safe threshold. They investigate and find complaints concentrated in a segment acquired through a partner promotion. Removing that segment and adding clearer unsubscribe options brings complaints to 0.04%.

Pro Tips

  • 1Make your unsubscribe link prominent—it's better to lose a subscriber than get a complaint
  • 2Set proper sending expectations at signup (frequency, content type)
  • 3Use list-unsubscribe header so Gmail shows an easy unsubscribe button
  • 4Monitor complaints by campaign and segment to identify problematic content or audiences

Common Mistakes to Avoid

Hiding unsubscribe links in tiny footer text, frustrating people into marking as spam
Sending too frequently without allowing preference management
Not honoring unsubscribe requests quickly enough (should be immediate)

Frequently Asked Questions

Related Terms

Sender Reputation

A score calculated by ISPs based on sending behavior, affecting inbox placement.

Unsubscribe Rate

The percentage of recipients who opt out of future emails. Healthy lists see 0.2-0.5% per send.