Hard Bounce

A hard bounce is a permanent email delivery failure caused by invalid, non-existent, or blocked recipient addresses. Unlike temporary delivery issues, hard bounces indicate the address should usually be removed from active sending lists immediately. High hard-bounce rates can damage sender reputation and reduce inbox placement across entire campaigns. Common causes include poor list sourcing, stale databases, data entry errors, and inadequate validation during signup. Strong email programs minimize hard bounces through confirmed opt-in, real-time form validation, and regular list hygiene workflows. Teams should monitor bounce reason codes, segment by acquisition source, and suppress repeated failures automatically. Reducing hard bounces is a core operational requirement for sustainable deliverability and scalable lifecycle marketing.