Summary
Determining the optimal number of soft bounces before suppressing a user is a complex task with no one-size-fits-all solution. ESPs vary in their internal handling, with some like Mailchimp setting a hard bounce after 15 soft bounces (or 7 with no history), while others (Brevo, Salesforce, Klaviyo) use lower thresholds. A general recommendation is 3-7 soft bounces, adjusted based on sending frequency. Experts emphasize monitoring bounce rates, analyzing bounce reasons, and understanding that 'soft bounce' categorizations can be misleading, masking underlying hard bounce issues. Proactive list hygiene, including double opt-in and regular list cleaning, is essential. A progressive backoff strategy and adapting to specific business needs is generally advised.
Key findings
- ESPs Differ: Different ESPs have different default thresholds for soft bounces before treating an address as a hard bounce.
- 3-7 is a common range: A range of 3-7 soft bounces is commonly cited as an appropriate suppression threshold, but requires adjustments.
- Soft Bounce Ambiguity: The term 'soft bounce' is not universally defined and can mask underlying hard bounce issues.
- Monitor Bounce Rates: Consistently monitoring bounce rates is crucial for informed decision-making.
- Proactive Hygiene: Proactive list hygiene (double opt-in, regular cleaning) significantly reduces soft bounce occurrences.
Key considerations
- Sending Frequency: Adjust the soft bounce threshold based on how frequently you send emails. More frequent sending may warrant a lower threshold.
- Bounce Reason: Analyze the specific reason for the soft bounce (mailbox full, server issue, etc.) to tailor your suppression strategy.
- SMTP Response Accuracy: Be wary of SMTP responses; they can sometimes be misleading.
- Progressive Backoff: Consider implementing a progressive backoff strategy, reducing send frequency before outright suppression.
- Monitor Trends: Monitor bounce trends and adjust your approach based on those trends.
- Business Needs: Align your suppression strategy with your overall business needs and risk tolerance.
- 5xx errors: Consider consecutive 5xx errors (internal server errors) over a period of days when deciding to suppress a user.
What email marketers say
11 marketer opinions
Determining the optimal number of soft bounces before suppressing a user requires a nuanced approach. Email marketers emphasize the importance of monitoring bounce rates, analyzing bounce reasons, and segmenting soft bounces based on type. Several sources suggest suppressing users after 3-7 consecutive soft bounces, but this threshold should be adjusted based on sending frequency, business needs, and deliverability goals. Implementing proactive list hygiene practices and leveraging automation can help optimize the process.
Key opinions
- Soft Bounce Threshold: A common recommendation is to suppress users after 3-7 consecutive soft bounces, but this number varies.
- Sending Frequency Impact: The appropriate soft bounce threshold is influenced by sending frequency; higher frequency may warrant a lower threshold.
- Bounce Reason Analysis: Analyzing bounce reasons is crucial for tailoring suppression rules and improving list hygiene.
- Proactive List Hygiene: Implementing double opt-in and regularly cleaning email lists are essential for effective bounce management.
Key considerations
- SMTP Response Accuracy: Be cautious when reacting to soft bounces, as SMTP responses can be misleading.
- Soft Bounce Segmentation: Consider segmenting soft bounces based on type (e.g., mailbox full vs. temporary server issue) to tailor suppression rules.
- Deliverability Goals: Align soft bounce suppression strategies with overall deliverability goals and business needs.
- Automation: Leverage automation to track soft bounces and automatically suppress contacts based on predefined criteria.
- Research Bounce Data: Research historical bounce data for your audience to optimize the soft bounce threshold.
Marketer view
Email marketer from Email Geeks warns about being careful when reacting to "soft bounces" due to potential misleading SMTP responses.
25 Dec 2021 - Email Geeks
Marketer view
Email marketer from Email Geeks defines a soft bounce as a rejection that is not a permanent reason.
28 Feb 2025 - Email Geeks
What the experts say
11 expert opinions
Determining the ideal number of soft bounces before suppression is complex and platform-dependent. ESPs like Mailchimp, Brevo, Salesforce, and Klaviyo have varying thresholds. A soft bounce is generally a temporary delivery issue that might resolve itself. Suppressing too aggressively risks losing valid recipients, so careful monitoring and a thoughtful approach are crucial. Factors like sending frequency should influence the decision. Furthermore, the reporting of soft bounces can be misleading as underlying hard bounce reasons might be obscured. Implement a progressive backoff strategy and analyze bounce trends before suppressing.
Key opinions
- ESPs Vary: Different ESPs (Mailchimp, Brevo, etc.) have different soft bounce thresholds before considering an address a hard bounce.
- Soft Bounce Definition: A soft bounce is a temporary delivery issue, like a full inbox, that might resolve itself.
- Risk of Over-Suppression: Suppressing after too few soft bounces can lead to the loss of valid, engaged recipients.
- Misleading Reporting: Soft bounce reporting may not always be accurate as it can mask underlying hard bounce reasons after retries.
Key considerations
- Sending Frequency: Adjust the soft bounce threshold based on sending frequency. Lower for frequent sending, higher for infrequent.
- Bounce Type: Consider the specific type of soft bounce (e.g., mailbox full) when deciding on suppression.
- Platform Categorization: Recognize that hard/soft bounce categorizations are arbitrary and platform-specific.
- Progressive Backoff: Implement a progressive back-off strategy, reducing sending frequency before final suppression.
- Trend Monitoring: Carefully monitor bounce trends and patterns to inform suppression decisions.
- Return Code Analysis: Analyze the return codes from soft bounces to determine whether an immediate block should be triggered.
Expert view
Expert from Email Geeks suggests considering consecutive 5xx errors over a period of days before suppressing an address, recommending X=3 and Y=15.
25 Feb 2023 - Email Geeks
Expert view
Expert from Spamresource.com suggests that when a soft bounce occurs, it should only trigger an immediate block if the specific return code indicates a high probability of continued failures. Otherwise, implement a progressive back-off strategy, reducing the sending frequency gradually. After a reasonable number of retries without success, then consider suppressing the user.
14 Nov 2023 - Spamresource.com
What the documentation says
5 technical articles
Email service providers like SendGrid, Mailjet, Amazon SES, SparkPost, and Postmark all handle soft bounces by retrying delivery for a certain period. They universally recommend monitoring bounce rates and adjusting sending practices accordingly to maintain a good sender reputation and overall deliverability.
Key findings
- Automatic Retry: ESPs automatically retry delivery for soft bounces.
- Temporary Failures: Soft bounces are defined as temporary delivery failures.
- Monitoring is Key: All ESPs highlight the importance of monitoring bounce rates.
- Reputation Impact: Consistently soft bouncing can negatively affect sender reputation.
Key considerations
- Adjust Sending: Adjust sending practices based on observed bounce trends.
- Review Bounce Codes: Carefully review bounce codes to understand the reasons for soft bounces.
- Exceeding Thresholds: Take action when bounce rates exceed acceptable thresholds to ensure deliverability.
- Feedback Monitoring: Monitor bounce feedback to inform suppression strategies and improve list hygiene.
Technical article
Documentation from SendGrid explains that it automatically handles bounces. For soft bounces, SendGrid retries delivery for up to 72 hours. If the email is still undeliverable after this period, it is considered a hard bounce.
3 Mar 2025 - SendGrid
Technical article
Documentation from SparkPost shares soft bounces are temporary delivery failures. They recommend reviewing bounce codes, monitoring rates, and adjusting sending policies based on observed trends.
29 Jul 2024 - SparkPost
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