What is Sender Reputation?

Sender reputation is the trust score that mailbox providers like Gmail and Outlook assign to your sending domain and IP address, based on how you send and how recipients respond. It's the single biggest factor in whether your emails reach the inbox or get diverted to spam — a strong reputation earns inbox placement, a damaged one quietly kills your results.

Reputation is built by consistent, moderate sending volume, high engagement (opens, replies), low bounce rates, and near-zero spam complaints. It's damaged by sudden volume spikes, emailing stale or purchased lists, and ignoring opt-outs. Because it accrues slowly and drops quickly, it rewards patience and punishes shortcuts.

Protecting sender reputation is why disciplined teams warm domains, cap volume, prune bad addresses, and end sequences with a breakup rather than emailing forever.