Also known as: Spam Complaint Rate, Abuse Rate
The percentage of recipients who mark your email as spam, a key signal mailbox providers use to judge senders.
Complaint rate is the share of delivered messages that recipients report as spam, usually by hitting the "Report Spam" button. Mailbox providers relay these reports through feedback loops (FBLs), and they weigh heavily in how providers judge you.
The accepted danger threshold is low — generally around 0.1%, or one complaint per thousand emails. Even a small spike can tip mailbox providers toward filtering your mail, because complaints are a direct statement from recipients that they did not want your message.
Complaints usually come from mailing people who did not clearly opt in, sending too often, or making unsubscribing hard. Clean opt-in practices, easy unsubscribes, and avoiding risky role accounts keep the rate down.
A trust score that mailbox providers assign to your sending IP and domain, which determines whether your mail reaches the inbox.
An address tied to a job function or team rather than a person, such as info@, support@, or sales@.
The ability of your email to actually reach recipients' inboxes rather than being blocked or filtered to spam.
See it in action
Check any address against BounceShift's multi-layer engine — syntax, MX, disposable, and role checks free, with full SMTP verification on signup.