Quick answer: A hard bounce is generally a permanent delivery failure, while a soft bounce is generally temporary. Marketers should suppress confirmed permanent failures, monitor repeated temporary failures and keep provider response codes. Exact meanings vary by receiving system, so use the SMTP response and your sending platform’s documentation.
Hard bounce vs soft bounce at a glance
| Type | Typical meaning | Common examples | Recommended response |
|---|---|---|---|
| Hard bounce | Permanent failure | Mailbox does not exist, domain cannot receive mail, permanent policy rejection | Suppress promptly and retain the reason. |
| Soft bounce | Temporary failure | Mailbox full, temporary server issue, message too large, rate limit | Follow a limited retry policy, then suppress repeated failures. |
The word “typically” matters. Providers do not always classify responses identically, and a code can reflect a policy decision rather than a simple mailbox state. Keep the original diagnostic response wherever your platform exposes it.
What a marketer should do after a hard bounce
- Stop normal campaign sends to the address.
- Add the address to the appropriate suppression list.
- Store the date, campaign, provider response and source.
- Correct the address only when a trusted first-party source supplies the correction.
- Review the acquisition path if one source produces an unusual concentration of failures.
Do not automatically resubscribe a corrected address or transfer preferences from one person to another. Your consent and identity rules still apply.
How to handle soft bounces
One temporary failure is not always a reason to remove a record permanently. Define a limited retry window in your sending platform, then suppress addresses that repeatedly fail according to your policy. Avoid aggressive retry behavior: it can create unnecessary traffic and obscure the real campaign signal.
Look at patterns, not just individual records. A spike at one receiving domain may point to throttling, authentication or reputation issues. A spike across an old segment may indicate list decay. A single oversized campaign may point to message construction.
Reduce avoidable bounces before sending
- Apply existing hard-bounce and unsubscribe suppressions before upload.
- Run a syntax check to identify malformed records.
- Review domain status and MX records.
- Use hard-bounce risk information as a pre-send decision signal.
- Segment older and unengaged records instead of mixing them into the main campaign.
Pre-send cleaning cannot predict every live delivery decision. Its value is reducing preventable data problems and making ambiguous records visible before they affect a large campaign.
A reporting view marketers can use
Report bounce rate by source, signup month, campaign type and receiving domain. Keep hard and soft failures separate. This helps acquisition teams see whether a form, import or partner source needs attention and helps campaign teams spot provider-specific problems.
Frequently asked questions
Should I retry a hard bounce?
Normally, a confirmed permanent failure belongs on a suppression list. Use the provider’s code and your platform’s rules rather than repeatedly retrying.
How many soft bounces are acceptable?
There is no universal number. Set a documented threshold using your platform’s capabilities, sending cadence and the actual response codes.
Does validation stop all bounces?
No. Mailbox state and provider decisions change. Validation reduces uncertainty; it does not guarantee acceptance.
Review your list before the next campaign
Follow the ListCleaner process to review a supported CSV before sending. Signup includes 100 free credits, and purchased credits do not expire. Compare credit packages for your list size.