Summary
The question of whether to suppress soft bounces for better email list hygiene is complex, with varying opinions among email professionals. While some systems automatically retry soft-bounced emails multiple times before considering them a permanent failure, the underlying reason for the bounce is crucial.Distinguishing soft from hard bounces is key, as temporary issues like a full mailbox differ significantly from permanent ones. Prematurely suppressing soft bounces can lead to inadvertently removing valid subscribers, potentially impacting your reach and engagement.
Key findings
- Bounce definitions: The terms 'soft' and 'hard' bounce are often used loosely. It is more effective to focus on the specific SMTP bounce codes and reasons rather than general categories.
- Temporary vs. permanent: Many soft bounces are temporary issues, such as a full mailbox or server overload. These can resolve over time, meaning the recipient might become reachable again.
- ESP handling: Most email service providers (ESPs) have built-in logic to handle soft bounces, retrying delivery multiple times before taking further action. Relying on their default processes is often sufficient for maintaining good list hygiene.
- Reputation impact: ISPs like Yahoo may 'soft bounce' for reputation reasons (e.g., rate limiting). Suppressing these immediately could lead to removing valid, engaged subscribers and losing a significant portion of your list.
Key considerations
- Understand bounce reasons: Dig into the specific error codes. This will provide more accurate insights than the generic soft bounce label. For more details, see our guide on which SMTP bounce codes to suppress.
- Monitor consecutive bounces: Instead of immediate suppression, monitor soft bounces over several sends. If an address consistently soft bounces (e.g., 3-5 times), it might be an indicator of a permanent issue. A good guide can be found on Email on Acid's list cleaning best practices.
- Consider engagement: For subscribers who repeatedly soft bounce due to 'mailbox full' errors, review their past engagement. If they haven't opened or clicked emails recently, their likelihood of becoming active again is low.
- Avoid over-suppression: Aggressive soft bounce suppression can lead to losing potentially valid contacts, harming your list size and overall reach. It is better to have a slightly higher soft bounce rate temporarily than to lose subscribers permanently.
What email marketers say
Email marketers often approach soft bounce management with a pragmatic view, balancing deliverability concerns with the desire to maintain a large, engaged list. Many rely on their ESP's default settings, which typically involve multiple retry attempts for soft bounces. The consensus leans towards cautious suppression, recognizing that not all soft bounces indicate a permanent issue.
Key opinions
- ESPs handle it: Many marketers trust their email service providers to manage soft bounces through built-in retry mechanisms, often seeing successful deliveries after initial bounces.
- Threshold-based suppression: Some marketers implement custom rules, converting soft bounces into hard bounces (and thus suppressing them) after a specific number of consecutive soft bounces (e.g., 3-5 attempts).
- Mailbox full: 'Mailbox full' is a common soft bounce reason, and marketers often observe that these addresses clear up over time, meaning they eventually receive emails.
- Focus on root cause: Instead of generic suppression, understanding the specific bounce reason (e.g., rate limiting, temporary server issue) helps in deciding the next steps.
Key considerations
- Distinguish consecutive vs. lifetime bounces: It's important to differentiate between an email address consistently soft bouncing on consecutive sends versus a cumulative count over its lifetime. The former indicates a more persistent issue.
- Consider temporary holds: For temporary soft bounce reasons, holding recipients out of mailings for a week or two before retrying can be effective without permanent suppression. Learn more about cleaning up soft bounces.
- Impact on deliverability: While soft bounces don't immediately damage sender reputation as severely as hard bounces, a consistently high volume can signal engagement issues or poor list quality. This can affect overall deliverability.
- List health assessment: If 'mailbox full' bounces are frequent, it may indicate a need to review list acquisition methods and engagement strategies to ensure subscribers are active and interested. Read about email hygiene definition and best practices.
Marketer view
Marketer from Email Geeks notes that they convert soft bounces to hard bounces after three email sends. This strategy was developed after observing that recipients who soft-bounced three times rarely engaged with future emails. Their experience with Eloqua's soft bounce definitions also revealed discrepancies, highlighting the need for custom rules based on analysis.
Marketer view
Marketer from Email Geeks suggests that their ESP (Pardot) tries to deliver soft bounces up to five times before classifying them as hard bounces. They are considering whether to intervene earlier but note that the current automated process seems to resolve many of these temporary issues, as the total number of hard bounces does not significantly increase over time.
What the experts say
Experts generally advocate for a nuanced approach to soft bounces, emphasizing the need to understand the underlying technical reasons rather than relying on generic classifications. They caution against aggressive suppression policies that could inadvertently remove valid subscribers, particularly when ISPs use soft bounces for reputation management or rate limiting. The consensus is to let sophisticated ESP logic handle retries and to focus on problematic, persistent bounce patterns.
Key opinions
- Bounce terms are misleading: The concepts of 'soft' and 'hard' bounces are often oversimplified and can be misleading without understanding the specific bounce reason (SMTP error code). A true understanding of bounce definitions is essential.
- ESPs handle it well: For most senders, relying on their ESP's default bounce handling—which typically involves multiple retries—is sufficient. Overriding this can sometimes lead to worse outcomes.
- ISP-specific behavior: Certain ISPs, like Yahoo, may soft bounce emails for reputation-related reasons (e.g., rate limiting), even for valid addresses. Suppressing these prematurely is detrimental.
- Focus on deliverability problems: Only consider custom soft bounce suppression rules if there's a specific, identifiable deliverability problem that generic handling isn't addressing.
Key considerations
- Risk of losing valid subscribers: Aggressive soft bounce suppression can lead to losing a significant portion of a valid email list, especially when bounces are due to temporary issues or ISP rate limits. This raises the question: is it bad to email addresses that keep soft bouncing?
- ESP reporting quality: The quality and specificity of soft bounce reporting vary widely among ESPs. What one ESP reports as a 'soft bounce' might already represent multiple retries and a permanent failure.
- Definition of permanent failure: By the time a 'soft bounce' is reported, it may already signify that the email has been retried enough times to be considered a permanent failure by the sending system. For more on this, check Word to the Wise on bounce nuances.
- Strategic re-engagement: If 'mailbox full' bounces are frequently observed for unengaged subscribers, it signals deeper list health issues rather than merely a temporary bounce. This is a crucial point for understanding bounce types.
Expert view
Expert from Email Geeks asserts that the terms 'soft' and 'hard' bounces are often imprecise. They explain that the true meaning of a bounce depends entirely on the specific reason provided in the bounce message. Any discussion that uses these terms without defining the underlying cause will inevitably lead to confusion and potentially incorrect actions.
Expert view
Expert from Word to the Wise explains that bounce handling is one of the most frustrating aspects of email deliverability. They often use visual aids to express the complexity and difficulty in navigating various bounce reasons, highlighting that a simple classification of 'soft' or 'hard' does not capture the full picture.
What the documentation says
Official documentation and industry standards often define bounces by their SMTP error codes, which provide granular detail beyond simple 'soft' or 'hard' labels. These resources typically recommend automated retry mechanisms for temporary errors and immediate suppression for permanent ones. The emphasis is on precise identification of the bounce reason to ensure optimal list hygiene and sender reputation.
Key findings
- SMTP codes are definitive: The RFC standards for email (e.g., RFC 5321) define various SMTP reply codes. These codes categorize bounce reasons, distinguishing between temporary failures (4xx codes) and permanent failures (5xx codes).
- Automated retries for temporary errors: Documentation typically advises email systems to retry sending messages that result in temporary errors, as the issue may resolve itself within a reasonable timeframe.
- Immediate suppression for permanent errors: For permanent errors (hard bounces), the recommendation is immediate removal of the address from active mailing lists to prevent future sending attempts and protect sender reputation.
- Impact on deliverability: A high soft bounce rate, especially if persistent, can still signal underlying issues that might affect sender reputation and inbox placement over time, even if not as immediately damaging as hard bounces. This is discussed in Mailgun's article on soft bounces.
Key considerations
- Klaviyo's approach: Klaviyo's help documentation states that a profile is suppressed due to a hard bounce or after seven consecutive soft bounces. This provides a clear, documented threshold for automated soft bounce suppression.
- Understanding 'mailbox full': While a 'mailbox full' error is a soft bounce, its persistence can indicate an abandoned account. Documentation advises monitoring engagement alongside bounce type to inform suppression decisions.
- Proactive list cleaning: Documentation on email list hygiene consistently recommends regular cleaning to remove inactive or problematic addresses, including those that consistently soft bounce. Refer to our guide on email verification best practices.
- SMTP bounce codes: Detailed documentation often provides a breakdown of various SMTP codes (e.g., 550 for permanent failures, 421 for temporary server issues) and how each should be handled programmatically by email platforms. This contrasts with anecdotal soft/hard bounce terms.
Technical article
Documentation from Klaviyo Help Center outlines their specific suppression policy for bounced emails. They state that a profile is automatically suppressed and removed from any lists if it experiences a hard bounce or accumulates seven consecutive soft bounces. This demonstrates a defined, automated threshold for soft bounce handling.
Technical article
Documentation from Email Industries explains that consistently monitoring bounce rates is essential for maintaining effective email deliverability. They classify hard bounces as permanent delivery errors requiring immediate removal from lists to prevent further damage to sender reputation.
Related resources
15 resources
Related pages
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