What is a soft bounce in email marketing?

A soft bounce indicates a temporary email delivery issue, such as a full inbox, an unavailable server, or a message exceeding size limits. It means the email was not delivered on the first attempt but might be deliverable later.

How many soft bounces before I should remove an email address?

There is no single magic number, but a common best practice is to remove an email address after 3-5 consecutive soft bounces within a specified timeframe, typically 21 days or more. If an email is delivered successfully, the counter for that address should reset. You can read more about determining how many soft bounces before suppressing a user .

What's the difference between a soft bounce and a hard bounce?

A soft bounce is a temporary delivery failure, while a hard bounce is a permanent delivery failure, indicating the email address is invalid, fake, or no longer exists. Hard bounces should be removed immediately from your list, whereas soft bounces might resolve over time.

Can soft bounces hurt my sender reputation?

Yes, a high volume of soft bounces, especially if they are persistent, can signal to Internet Service Providers (ISPs) that your list quality is poor or that you're sending to unengaged recipients. This can negatively impact your sender reputation and lead to more emails going to spam or being blocklisted (or blacklisted).

How can I prevent soft bounces from happening in the first place?

Prevention strategies include maintaining good email list hygiene through regular cleaning, using double opt-in for new subscribers, properly authenticating your domain with SPF, DKIM, and DMARC, and avoiding sudden spikes in sending volume or overly large email sizes. You can check our guide on best practices for email verification and reducing bounces .

What is the best practice for cleaning up soft bounces in email marketing? - Sender reputation - Email deliverability - Knowledge base

When managing email marketing campaigns, encountering bounces is inevitable. While hard bounces signify permanent delivery failures, soft bounces indicate temporary issues. Cleaning up soft bounces is crucial for maintaining a healthy email list and strong sender reputation. Ignoring them can negatively impact your deliverability and overall campaign performance.

Understanding the nuances of soft bounces and implementing effective cleanup strategies is vital for any email marketer. It helps ensure your messages reach their intended recipients, improving engagement and return on investment.

Understanding soft bounces

Soft bounces occur when an email is temporarily undeliverable. Unlike hard bounces, which mean the email address is invalid or no longer exists, soft bounces suggest a transient problem. These issues can often resolve themselves, allowing future emails to be delivered.

Common reasons for a soft bounce include a recipient's mailbox being full, the server being temporarily down, or the message size exceeding the recipient's server limits. Sometimes, temporary blocklists (or blacklists) can also cause soft bounces, especially if an IP address is briefly flagged. It is important to identify the specific reason for a soft bounce to determine the appropriate course of action. For more information, you can read about understanding soft and hard bounced emails.

Bounce reason	Description	Action
Mailbox full	Recipient's inbox has reached its storage limit.	Wait and retry, monitor for repeat occurrences.
Server down/unavailable	Recipient's mail server is temporarily offline or overloaded.	Retry later, often resolves automatically.
Message too large	Email size (including attachments) exceeds server limits.	Review campaign content, reduce attachment sizes.
Temporary blocklist	Sender's IP or domain is temporarily on a blocklist.	Investigate blocklist status, improve sending practices.

Implementing a soft bounce cleanup strategy

A structured approach to managing soft bounces is essential. Simply removing an address after one soft bounce is often too aggressive, as the issue might be temporary. Many email service providers (ESPs) automatically retry sending soft-bounced emails for a period. The key is to establish a rule that balances patience with proactive list hygiene.

A common and effective practice is to implement a consecutive soft bounce rule. For example, some experts recommend removing a contact only after they have experienced at least three consecutive soft bounces over a period, such as 21 days. This approach provides multiple opportunities for the temporary issue to resolve while preventing endless attempts to an unresponsive address.

The consecutive soft bounce rule

It is crucial that if a message does successfully deliver, the counter for consecutive soft bounces for that address is reset. This ensures that a recipient who was temporarily unavailable, but then becomes reachable again, is not mistakenly flagged for removal. Tailoring this rule to your specific sending volume and audience engagement patterns can further optimize its effectiveness. You can explore recommended soft bounce suppression logic for email.

Consider segmenting users who repeatedly soft bounce. This allows you to analyze their behavior more closely. If an email address consistently soft bounces over several months, even if not strictly consecutive, it might indicate a more persistent problem or a less engaged subscriber. You can learn more about a reasonable soft bounce tolerance in email marketing.

Proactive measures to reduce soft bounces

While cleaning up soft bounces is reactive, preventing them through proactive measures is even better. Maintaining a healthy email list is fundamental to reducing your overall bounce rate, including soft bounces. This involves regular email list cleaning and verification. Reducing your email bounce rate to 2% or less is ideal.

Prevention

Regular list hygiene: Periodically remove inactive or unengaged subscribers. This reduces the likelihood of hitting full mailboxes or outdated addresses. Learn about the best way to clean an email list.
Double opt-in: Require new subscribers to confirm their subscription. This ensures genuine interest and valid email addresses, reducing initial bounce rates.
Email authentication: Properly configure SPF, DKIM, and DMARC to build and maintain sender reputation. Strong authentication can prevent emails from being flagged as suspicious or spam, which can sometimes lead to soft bounces from strict email providers. Our blog discusses why your emails are going to spam and how to fix it.
Content and sending volume: Optimize email content to avoid spam triggers. Maintain a consistent and appropriate sending volume, sudden spikes can sometimes lead to temporary blocking by ISPs. Consider the impact of large attachments on delivery.

Cleanup

Consecutive bounce rule: Implement a system that tracks consecutive soft bounces. For example, remove an address after 3-5 consecutive soft bounces within a defined timeframe.
Monitor bounce categories: Not all soft bounces are equal. Some, like 'mailbox full,' are temporary, while others might signal a more persistent issue. Categorize bounces to apply different suppression rules.
Segment and re-engage: Instead of immediate removal, segment consistently soft-bounced contacts. Try sending them re-engagement campaigns or alternative communication methods.
Integrate with CRM/ESP: Many email marketing platforms (ESPs) and CRM systems offer automated bounce management features. Leverage these to streamline the cleanup process and ensure consistency. Learn how Salesforce Marketing Cloud handles email bounces.

Advanced strategies and monitoring

Beyond basic cleanup rules, advanced strategies can further refine your approach to soft bounces. Understanding the root cause of persistent soft bounces often requires deeper analysis of bounce codes. Internet service providers (ISPs) often provide specific codes detailing why an email was not delivered.

Monitoring your sending reputation is paramount. A sudden increase in soft bounces, particularly those related to temporary blocks or rate limiting, can be an early indicator of reputation issues. Tools for blocklist (or blacklist) monitoring and DMARC monitoring provide crucial insights into how your emails are performing across various ISPs. For example, you can get insights from Google Postmaster Tools on your domain reputation.

Example DMARC record to receive aggregate reports

v=DMARC1; p=none; rua=mailto:dmarc_reports@yourdomain.com;

This record, placed in your DNS, allows you to receive daily DMARC reports that include aggregated data on email authentication results, including information about failed deliveries, which can help in identifying patterns related to soft bounces. For more technical insights, you can explore how to fix common DMARC issues.

Views from the trenches

Best practices

Implement a rule to remove contacts after a specific number of consecutive soft bounces, such as three to five within a set timeframe.

If an email successfully delivers, reset the soft bounce counter for that contact to ensure temporary issues don't lead to premature removal.

Common pitfalls

Removing contacts after just one or two soft bounces is often too aggressive and can lead to losing valuable, reachable subscribers.

Failing to differentiate between various types of soft bounces means applying a one-size-fits-all rule when different issues require different responses.

Expert tips

Create a segment for contacts who consistently soft bounce (e.g., over 95% of sent emails in three months) to review them individually for persistent issues.

Balance strict list hygiene with the understanding that some bounces are truly temporary, ensuring you do not unnecessarily remove viable contacts.

Marketer view

Marketer from Email Geeks says a rule of at least three consecutive soft bounces over at least 21 days has proven reasonable for their cleanup strategy.

Feb 1, 2023 - Email Geeks

Marketer view

Marketer from Email Geeks mentions that this rule balances the need for list hygiene with the understanding that temporary issues can cause bounces.

Feb 1, 2023 - Email Geeks

Conclusion: Maintaining a healthy email ecosystem

Effectively cleaning up soft bounces is a continuous process that combines reactive cleanup rules with proactive deliverability best practices. By carefully defining your soft bounce suppression logic (e.g., based on consecutive bounces), leveraging email authentication (like DMARC), and consistently monitoring your email health, you can significantly reduce their impact.

This dedication to list hygiene and sender reputation management not only improves your inbox placement but also maximizes the effectiveness of your email marketing efforts. Staying vigilant and adapting your strategies will lead to a more efficient and successful email program.