Soft bounce
In short
A soft bounce is a temporary failure to deliver an email. The address exists, but something prevented delivery at that moment, such as a full mailbox, a server outage, or a message that is too large.
Unlike a hard bounce, a soft bounce does not mean the address is bad. Most email platforms retry for a period, then treat repeated soft bounces as a problem and may suppress the address.
Common causes of soft bounces
- Full mailbox: The recipient's inbox is over its storage limit.
- Server issues: The receiving server is down or overloaded.
- Message too large: Big attachments can exceed limits.
- Auto-reply or filters: Temporary policies or greylisting can delay acceptance.
How to handle soft bounces
Let the platform retry
Most tools retry a few times over a day or two. Avoid manual resends that look like spam.
Set a limit
If an address soft bounces across several separate sends, treat it as unreliable and suppress it. Say your rule is three failed campaigns in a row; that threshold is an example, so tune it to your tool.
Check your own content
Heavy attachments and image-laden emails raise the chance of a soft bounce. Link to files instead.
Why soft bounces matter for outbound
A few soft bounces are normal. A rising rate can mean stale data or a sending-reputation problem on your side. Track them next to hard bounces and replies so a trend is visible early.
Soft bounce vs. hard bounce
A soft bounce is temporary and may resolve. A hard bounce is permanent and needs immediate removal. A repeated soft bounce can effectively become a hard one once you stop trusting the address.
Soft bounce FAQs
What is a soft bounce in email?
A soft bounce is a temporary email delivery failure. The address is valid, but the message could not be delivered at that moment because of something like a full inbox, a server outage, or an oversized message.
What causes a soft bounce?
Common causes include a recipient mailbox that is full, a temporarily unavailable receiving server, a message or attachment that is too large, and temporary filtering such as greylisting. These conditions often clear without any action from the sender.
Should you resend after a soft bounce?
Usually your email platform retries automatically for a limited period. Avoid repeated manual resends. If an address keeps soft bouncing across several separate campaigns, suppress it or verify it before sending again.
Do soft bounces hurt sender reputation?
Occasional soft bounces have little effect, but a persistently high rate can suggest poor list quality and may influence how mailbox providers treat your mail. Monitor them alongside hard bounces and clean lists regularly.
