What is a soft bounce?

Soft bounce

A soft bounce is an email that reaches the recipient's mail server but gets returned undelivered due to a temporary issue. The address is valid and the server recognized it, but something prevented delivery in that moment.

Think of it like calling someone whose phone goes straight to voicemail because their battery died. The number works; they just can't pick up right now.

Soft bounce vs. hard bounce

The difference comes down to temporary versus permanent.

A soft bounce means delivery failed this time, but the email address is still valid. Your email platform will typically retry delivery over the next 24-72 hours before giving up.

A hard bounce means the address is permanently unreachable: the email doesn't exist, the domain is invalid, or there's a typo in the address. These contacts should come off your list immediately. Continuing to send to them damages your sender reputation and hurts future deliverability.

Soft bounce:

• Temporary failure (full inbox, server down, message too large)
• Platform retries automatically
• Monitor but don't remove immediately

Hard bounce:

• Permanent failure (invalid address, domain doesn't exist)
• Remove from list right away
• Continuing to send hurts your reputation

Common causes of soft bounces

Recipient's inbox is full. The mailbox hit its storage limit. Once they clear space, your next email should land.

Server is temporarily unavailable. The receiving mail server might be down for maintenance or experiencing technical issues. This usually resolves within hours.

Message is too large. Heavy images or attachments can exceed size limits. Most inboxes cap messages around 25MB, so keep emails lean.

Content triggered a filter. Some servers temporarily reject emails that look suspicious. Your content may have tripped a security rule without being actual spam.

Authentication issues. If your SPF, DKIM, or DMARC records aren't configured correctly, some servers will defer your messages rather than accept them. Use a free SPF checker to verify your setup.

How email platforms handle soft bounces

When an email soft bounces, your platform doesn't give up immediately. ActiveCampaign and most ESPs retry delivery multiple times over 24-72 hours before marking the send as failed.

If the same address soft bounces repeatedly across multiple campaigns, most platforms eventually treat it like a hard bounce and suppress future sends. This protects your deliverability from addresses that consistently fail.

Check your campaign reports for soft bounce details. Look for patterns: if bounces cluster around a specific domain, that domain's server may be blocking your sends or experiencing ongoing issues.

How to reduce soft bounces

1. Start with list hygiene. Remove contacts who haven't engaged in months. An abandoned inbox is more likely to hit storage limits or belong to a defunct domain.
2. Authenticate your sending domain. Proper SPF, DKIM, and DMARC setup tells receiving servers you're legitimate, reducing temporary rejections.
3. Watch your email size. Strip unnecessary images, avoid large attachments, and use hosted links instead of embedded files.
4. Segment by engagement. Sending to your most active subscribers first builds positive signals with inbox providers, which improves delivery rates for the rest of your list. Learn more about email engagement and deliverability.
5. Monitor your bounce rate. Keep your combined bounce rate (soft and hard) below 2%. Consistently higher rates signal list quality problems that can affect long-term deliverability.

FAQs

What's an acceptable soft bounce rate?
Keep your overall bounce rate below 2%. If you're consistently above that, review your list hygiene and sending practices.

Should I remove soft-bounced contacts from my list?
Not immediately. Soft bounces are temporary. However, if the same contact soft bounces across several campaigns, consider suppressing them or reaching out through another channel.

Can soft bounces hurt my sender reputation?
A few won't cause problems. But a pattern of high soft bounce rates signals to inbox providers that your list quality may be poor, which can affect deliverability over time.

How do I find out why an email soft bounced?
Check your campaign reports. Most platforms show bounce codes and reasons, like "mailbox full" or "server temporarily unavailable."

What's the difference between a bounce and a blocked email?
A bounce means the server couldn't accept the message. A block means the server actively rejected it, often due to reputation issues or content filtering. Both appear in your bounced email metrics.

Ready to see your bounce rates drop? Start a free ActiveCampaign trial and get deliverability tools built in.