The spam complaint rate is the share of measured emails that recipients report as spam. Unsubscribing removes someone from a mailing list. A complaint reports the message to the recipient’s email provider.
How to read the number
For a simple example, divide complaints by the messages counted in the same report and multiply by 100. Two complaints out of 4,000 measured messages give 0.05 percent. The denominator and the complaints you can see depend on the data source. Google Postmaster Tools reports its own rate for Gmail.
What should you do if the rate rises?
Start by comparing the same data source over similar sending periods. Then check which mailings, signup sources, or frequency changes coincide with the rise. A low complaint rate alone does not demonstrate good inbox placement.
