What’s the difference between spam placement rate and complaint rate?

Different metrics measuring different things:

Spam placement rate: Percentage of delivered messages that land in spam folder. Measures filter decisions.

Complaint rate: Percentage of recipients who click "Report Spam" or "Junk" button. Measures user dissatisfaction.

You can have low complaints but high spam placement (filters block you before users see it).

You can have low spam placement but high complaints (messages reach inbox but users reject them).

Both matter. High complaints will eventually cause high spam placement. High spam placement prevents complaints but also prevents engagement.

Placement is the harbor's decision. Complaints are the merchants' judgment of your goods.