What is sender reputation?

Sender reputation is the cumulative trust score that internet service providers (ISPs) like Gmail, Microsoft, Yahoo, and Apple assign to your sending domain and your sending IP address. It is not one number. Each ISP maintains its own internal scoring. The inputs are largely the same across providers.

Inputs that drive sender reputation:

• Authentication compliance. SPF, DKIM, DMARC passing consistently.
• Bounce rate. Invalid sends divided by total sends.
• Complaint rate. Recipients hitting Mark as Spam.
• Engagement rate. Opens, clicks, replies, forwards.
• Spam-trap hits. Any is bad. Sustained is catastrophic.
• Sending consistency. Predictable volume over time.
• Account history. Long-running clean accounts get more grace than new ones.

Reputation determines inbox placement. Even with perfect content, a sender with damaged reputation lands in spam. Even with mediocre content, a sender with strong reputation lands in the inbox. It is the foundation everything else builds on.

Reputation is built deliberately and damaged quickly. A single major mistake, like sending to a large unverified list or hitting multiple spam traps, can undo months of careful sending. See how to build sender reputation.