Complaint rate measures the percentage of your delivered emails that recipients have marked as spam or otherwise complained about through a Complaint Feedback Loop (CFBL). This is one of the most important metrics for maintaining good email deliverability and sender reputation, alongside metrics like open rate and click rate.
A high complaint rate can lead to:
- Your emails being filtered to spam folders
- Reduced deliverability across your entire subscriber base
- Potential account restrictions from email service providers
How it's calculated
Complaint rate is calculated by dividing the number of complaints by the number of delivered emails:
For example, if 1,000 emails were delivered and 5 recipients marked them as spam, your complaint rate would be 0.5%.
What's a good complaint rate?
Email industry standards suggest:
| Rating | Complaint Rate |
|---|---|
| Excellent | Below 0.1% |
| Good | 0.1% - 0.2% |
| Concerning | 0.2% - 0.5% |
| Problematic | Above 0.5% |
If your complaint rate is above 0.2%, you should take a closer look at your content, sending frequency, and subscriber acquisition methods.
Reducing your complaint rate
Buttondown has specific deliverability standards that all newsletters must meet, including a complaint rate of 0.1% or lower.
If you're seeing a higher than desired complaint rate, consider these steps:
- Make unsubscribing easy: Place an obvious unsubscribe link at the top of your emails
- Set clear expectations: Let subscribers know what content they'll receive and how often
- Segment your audience: Send relevant content to specific segments rather than blasting everyone
- Clean your list: Remove long-term inactive subscribers periodically
- Avoid spam triggers: Be cautious with all-caps, excessive exclamation points, and spam-triggering words
- Follow the rules: Ensure you're complying with Buttondown's Acceptable Use Policy
Monitoring your complaint rate regularly is essential for maintaining a healthy newsletter and ensuring your emails reach your subscribers' inboxes. You may also want to track your permanent failure rate as another key deliverability metric.