Amazon SES Blog

Email Definitions: Complaint Rate

Now that we’ve talked about complaints and feedback loops, we are ready to discuss complaint rates.

As a reminder, a complaint occurs when an email recipient marks an email message as spam by clicking “This is spam” or “send to spam folder” in their web email client. The Internet Service Provider (ISP) records this as a complaint. If the ISP has a feedback loop in place with the Email Service Provider (ESP), the ESP is notified. If you are using Amazon SES, then Amazon SES is the ESP and it forwards the complaint to you by email or by using an Amazon Simple Notification (SNS) topic, depending on how you have your system set up. (For more information, see Handling Bounces and Complaints.)

You can calculate the overall complaint rate by dividing the total number of complaints by the number of emails sent:

Complaint rate

However, this doesn’t necessarily give you an accurate idea of the complaint rates that ISPs are seeing, because not all ISPs have feedback loops set up with your ESP (e.g., Amazon SES). In order to get a better picture, you can calculate your complaint rate per ISP or domain (e.g., yahoo.com).  For each domain or ISP, you would use something like this:

Yahoo's complaint rate

Your target for each ISP that is sending you complaints should be for each ISP’s complaint rate to be less than 0.1%. ISPs are trying to make their users happy, so they take complaints very seriously. Try to keep your complaint rates very low, even if you need to calculate them some other way.

If you trace a complaint back to a specific recipient, you should remove that recipient from your list so that they don’t get that type of email from you again. In other words, if you receive a complaint from a recipient for a marketing email, you should stop sending them your marketing email but continue to send them transactional email. For more information about how to keep complaint rates low, see Amazon Simple Email Service Email Sending Best Practices. Happy emailing!

Note added 2015-12-04: For SES specifically, we expect our senders’ complaint rates to remain below 0.1%. Senders with a complaint rate exceeding 0.5% risk suspension.