Complaint rate

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

Complaint rate is calculated by dividing the number of complaints by the number of delivered emails:

Complaint Rate = Number of Complaints / 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%.

Email industry standards suggest:

If your complaint rate is above 0.2%, you should take a closer look at your content, sending frequency, and subscriber acquisition methods.

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:

1. Make unsubscribing easy: Place an obvious unsubscribe link at the top of your emails
2. Set clear expectations: Let subscribers know what content they'll receive and how often
3. Segment your audience: Send relevant content to specific segments rather than blasting everyone
4. Clean your list: Remove long-term inactive subscribers periodically
5. Avoid spam triggers: Be cautious with all-caps, excessive exclamation points, and spam-triggering words
6. 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.