Complaint rate, often called spam rate, is the share of recipients who mark your email as spam. A complaint is one of the strongest negative signals a mailbox provider receives, because it comes directly from the person the email was meant for. Even a small number of complaints relative to your volume can push future mail towards the spam folder.
Gmail and Yahoo expect bulk senders to keep their spam rate below 0.3%, and recommend staying under about 0.1%. Those figures sound tiny, but they mean three complaints in every thousand delivered emails is already a problem. Google’s spam rate, shown in Postmaster Tools, is calculated from users who reported mail that reached their inbox, so it can look different from the figure your email platform reports.
The causes are usually predictable: people who don’t remember subscribing, lists that were bought or collected without clear consent, sudden jumps in frequency, an unsubscribe link that is hard to find, or content that doesn’t match what people signed up for. Festival seasons are a classic risk, when daily sale emails go to subscribers who usually get one a month.
To lower the rate, make unsubscribing obvious and instant, use one-click unsubscribe headers, send most often to people who engage, and suppress anyone who complains. A preference centre that lets people choose fewer emails or pause for a while gives frustrated readers an alternative to the spam button.
A Delhi fashion label sends 50,000 emails over Navratri and receives 200 complaints, a 0.4% rate, after switching from weekly to daily emails. For Diwali it sends daily emails only to people who clicked in the last 60 days and weekly ones to everyone else, and complaints fall below 0.1%.
MailNesto shows your complaint rate for the last 30 days on the deliverability page, stops emailing anyone who reports spam, and supports one-click unsubscribe so people can leave without using the spam button.