---
title: "What is Hard bounce?"
url: "https://lookvalid.com/glossary/hard-bounce.md"
canonical_url: "https://lookvalid.com/glossary/hard-bounce"
last_updated: "2026-10-18"
type: "conceptual"
summary: "A hard bounce is a permanent delivery failure, usually because the address does not exist or the domain cannot receive mail."
related: ["https://lookvalid.com/glossary/smtp-verification.md", "https://lookvalid.com/glossary/spam-trap.md", "https://lookvalid.com/glossary/catch-all.md", "https://lookvalid.com/products/email-domain-check.md"]
---

# What is Hard bounce?

A hard bounce is a permanent delivery failure, usually because the address does not exist or the domain cannot receive mail.

It differs from a soft bounce, a temporary failure such as a full mailbox or a busy server that may succeed on retry. Mail servers signal hard bounces with permanent error codes in the 500 range.

Mailbox providers track how often you send to dead addresses. A high hard-bounce rate harms your sender reputation, so remove hard-bounced addresses at once and validate lists before large sends.

## Related

- [What is SMTP verification?](https://lookvalid.com/glossary/smtp-verification.md)
- [What is Spam trap?](https://lookvalid.com/glossary/spam-trap.md)
- [What is Catch-all?](https://lookvalid.com/glossary/catch-all.md)
- [Email Domain Check API](https://lookvalid.com/products/email-domain-check.md)