---
title: "Soft bounce"
description: "A soft bounce is a temporary rejection of an email by the recipient's server. Learn the causes and how it differs from a hard bounce."
url: "https://nodea.io/en/glossary/soft-bounce"
lang: "en"
updated: "2026-07-13"
---

# Soft bounce

> A soft bounce is a temporary email delivery failure — the recipient's server rejects the message for a transient reason, but the address stays valid.

A **soft bounce** is a temporary email delivery failure in which the recipient's server accepts the attempt but rejects it for a transient reason. Unlike a [hard bounce](https://nodea.io/en/glossary/hard-bounce), the address remains valid and existing — the problem is momentary, so a later send attempt has a real chance of success.

## What a soft bounce is

When the sender's server tries to deliver a message over the [SMTP](https://nodea.io/en/glossary/smtp) protocol, the recipient's server replies with a status code. Codes in the 4xx range indicate a temporary error and are exactly what produces a soft bounce. The most common causes are:

- a full inbox (storage limit exceeded),
- a briefly unavailable or overloaded mail server,
- an oversized message or attachment,
- a temporary hold by a spam filter (greylisting).

Mail-sending systems usually retry delivery of a soft-bounced message automatically for some time. If the address keeps bouncing after a series of attempts, it is treated as inactive and reclassified as a hard bounce so it does not damage the sender's reputation.

## Soft bounce in practice

Distinguishing soft from hard bounces is crucial in [email marketing](https://nodea.io/en/glossary/email-marketing) and when analyzing [deliverability](https://nodea.io/en/glossary/email-deliverability). Mailing platforms report soft bounces separately so a marketer does not immediately delete valid contacts, only monitors those that bounce repeatedly. Keeping the [bounce rate](https://nodea.io/en/glossary/bounce-rate) low and quickly retiring problematic addresses protects the sending domain's reputation and keeps campaign performance high.

### How is a soft bounce different from a hard bounce?

A soft bounce is a transient problem — a full mailbox, a briefly unavailable server or an oversized attachment — after which retrying is worthwhile. A hard bounce is a permanent rejection, such as a non-existent address, and that contact should be removed from the list immediately.

### Does a soft bounce hurt sender reputation?

Occasional soft bounces are normal and harmless. The trouble starts when the same address soft-bounces repeatedly — mail systems then treat it as inactive, which lowers deliverability. After a run of failed attempts, that contact is best retired.

## Related

- [Hard bounce](https://nodea.io/en/glossary/hard-bounce)
- [Bounce rate](https://nodea.io/en/glossary/bounce-rate)
- [Deliverability](https://nodea.io/en/glossary/email-deliverability)
- [Email marketing](https://nodea.io/en/glossary/email-marketing)
- [SMTP](https://nodea.io/en/glossary/smtp)

---

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