Spam complaint rate is the percentage of delivered emails that recipients mark as spam, calculated as spam complaints divided by emails delivered. Mailbox providers like Gmail and Outlook watch it closely — keeping it below roughly 0.1% is essential to stay in the inbox.
Why it matters so much
Even a small spike in complaints tells providers your mail is unwanted, which sends future campaigns to spam — for your whole list, not just the complainers. It is one of the fastest ways to damage deliverability and your sender score.
How to keep it low
Only mail people who opted in, make unsubscribing easy and obvious, keep a consistent sending frequency, and set clear expectations at sign-up. Our guide shows how: reduce your spam complaint rate below 0.1%, plus tips on avoiding spam folders.
How Mailpro helps
Mailpro pairs authenticated sending with one-click unsubscribe and anti-spam tools so complaints stay low and your mail keeps landing. Related: graymail and email blacklist.
Mailpro and spam complaints
Stay under the complaint threshold, stay in the inbox
Authenticated sending, easy unsubscribe, and reputation monitoring keep your complaint rate low so your campaigns keep landing.