Summary
Understanding soft bounces and setting an appropriate tolerance is crucial for maintaining strong email deliverability and sender reputation. Soft bounces indicate temporary delivery issues, unlike hard bounces which signify permanent failures. While hard bounces require immediate removal from your list, soft bounces often resolve themselves over time, necessitating a strategic approach to their management.
Key findings
- Definition: A soft bounce occurs when an email reaches the recipient's server but is temporarily undeliverable, often due to a full inbox, server issues, or message size limits.
- Tolerance levels: Many email service providers (ESPs) and industry experts suggest a soft bounce tolerance of 7 to 15 consecutive bounces before an address is suppressed.
- Impact on reputation: Consistently high soft bounce rates can negatively impact your sender reputation, signaling to ISPs that your list may contain outdated or problematic addresses, even if issues are temporary.
- Distinction from hard bounces: It's vital to differentiate between soft and hard bounces, as they require different handling strategies. Hard bounces demand immediate removal, while soft bounces warrant a period of retry.
- Time dimension: The duration over which soft bounces accumulate is as important as the count itself. Seven soft bounces in a single day are different from seven over several weeks.
Key considerations
- Monitoring bounce rates: Regularly monitor your overall bounce rate, aiming for less than 2-3%. High bounce rates (including soft bounces) can lead to blocklisting.
- Automated suppression: Implement automated systems to suppress addresses that hit your defined soft bounce tolerance. This ensures list hygiene and protects your sender reputation.
- List cleaning: Proactive list cleaning can reduce soft bounces by identifying and removing invalid or problematic email addresses before they become consistent issues. Learn more about email list cleaning services.
- Understanding bounce codes: Familiarize yourself with different email bounce codes to better diagnose the root cause of soft bounces and take appropriate action. A comprehensive guide on hard vs soft bounces can also be helpful from resources like Business News Daily.
- Sender volume: Sudden spikes in email sending volume can sometimes trigger soft bounces as ISPs temporarily throttle incoming mail, impacting your deliverability. Consider best practices for email frequency and volume management to mitigate this.
What email marketers say
Email marketers often navigate the complexities of soft bounce tolerance based on their ESP's policies and practical experience. While specific numbers vary, there's a general consensus on the need to manage these bounces to protect sender reputation and optimize campaign performance. The duration and context of soft bounces are frequently highlighted as key factors.
Key opinions
- Common tolerance: A soft bounce tolerance of around 7 consecutive bounces is widely considered reasonable by many marketers.
- Consecutive counts: The consensus leans towards tracking consecutive soft bounces rather than lifetime counts, as this directly indicates ongoing delivery issues for a specific address.
- Time sensitivity: Marketers emphasize that the time frame matters. Seven bounces in one day are far more concerning than seven bounces spread across several weeks or months, as the latter indicates a more gradual or intermittent issue.
- Provider-specific rules: Many acknowledge that ESPs (email service providers) have their own internal soft bounce management rules, which marketers often adhere to, such as Mailchimp allowing 7 soft bounces for inactive subscribers and up to 15 for active ones, as noted by Igniting Business.
- Differentiation from retries: There's a need to distinguish soft bounce tolerance from retry intervals. Tolerance relates to suppressing an address after multiple failed attempts across different sends, while retry intervals refer to temporary re-attempts within a single send.
Marketer view
Email marketer from Email Geeks observes that their vendor (Klaviyo) maintains a policy of allowing 7 'soft' bounces consecutively for an email address before it is removed from the active sending list. This provides a clear guideline for how temporary delivery issues are managed by their platform.
Marketer view
Email marketer from Email Geeks clarifies that the 7 soft bounces mentioned by a peer refer to consecutive bounces, not lifetime bounces. This distinction is important because it implies that only subsequent failures matter, not a cumulative tally over an indefinite period.
What the experts say
Email deliverability experts emphasize that while some soft bounces are inevitable, effective management is key to protecting sender reputation. They often highlight the nuances of bounce reasons, the importance of historical engagement, and the specific policies of Internet Service Providers (ISPs) in determining an optimal soft bounce tolerance.
Key opinions
- Context matters: Experts stress that a static number for soft bounce tolerance might be misleading. The context of the bounce (e.g., specific error code, frequency of bounces for that address, time since last successful delivery) is more important.
- Dynamic thresholds: Instead of a fixed number, experts often suggest dynamic soft bounce thresholds that adjust based on subscriber engagement and the historical deliverability of the email address.
- Risk assessment: Delaying the suppression of a consistently soft-bouncing address poses a risk to sender reputation. ISPs may interpret repeated attempts to undeliverable addresses as poor list hygiene or even spamming behavior.
- ISP feedback loops: Leveraging ISP feedback loops for bounce data provides critical insights that can help fine-tune soft bounce management strategies beyond simple numerical tolerances.
- Long-term deliverability: The primary goal of managing soft bounces is to protect long-term deliverability. This sometimes means suppressing addresses proactively even if there's a slight chance they might eventually become deliverable.
Expert view
An expert from SpamResource highlights that sudden increases in email sending volume are a primary cause for most soft bounces today. ISPs may temporarily block or defer emails from senders whose volume spikes unexpectedly, indicating that consistent sending patterns are crucial.
Expert view
An expert from Word to the Wise cautions that ignoring soft bounces for too long can be detrimental. They suggest that persistent soft bounces, even if technically temporary, can signal neglect of list hygiene and lead to more serious reputation issues over time.
What the documentation says
Official documentation from various email platforms and industry bodies provides guidelines and best practices for managing soft bounces. While specific numerical tolerances may vary, the underlying principles revolve around preserving sender reputation and ensuring deliverability by promptly addressing temporary delivery issues.
Key findings
- Temporary nature: Documentation consistently defines soft bounces as temporary failures, implying that retries are permissible and expected.
- Retry algorithms: ESPs' documentation often details their internal retry algorithms, which typically include increasing delays between attempts to allow temporary issues to resolve.
- Suppression criteria: Many platforms outline specific criteria, such as a number of consecutive soft bounces or a period of inactivity, that trigger the suppression or removal of an email address.
- Reputation impact: Documentation frequently warns that failing to manage soft bounces can lead to negative sender reputation, increased spam complaints, and even blocklisting (or blacklisting).
- Bounce code interpretation: Official resources often provide comprehensive lists of SMTP bounce codes and their meanings, distinguishing between transient (4xx) and permanent (5xx) errors, which is crucial for determining soft bounce tolerance.
Key considerations
- Adherence to ISP policies: It is critical to understand and adhere to the specific soft bounce management policies of major ISPs, as documented by their postmaster sites. Ignoring these can lead to throttles or blocks.
- Bounce logs review: Regularly reviewing SMTP bounce logs and understanding the specific reasons for soft bounces (e.g., mailbox full, message too large) helps in refining your sending strategy.
- Engagement signals: Documentation often implies that historical engagement can influence how soft bounces are treated. Addresses with recent engagement might receive more retries.
- Compliance with standards: Ensure your bounce handling practices comply with industry standards and RFCs related to email delivery, which dictate how mail servers should respond to temporary errors.
- Automated re-engagement: Consider implementing automated re-engagement workflows for addresses that soft bounce repeatedly, attempting to confirm their validity before final suppression.
Technical article
Mailchimp's documentation specifies that their system will allow 7 soft bounces for an email address with no subscriber activity and up to 15 soft bounces for contacts with previous subscriber activity before suppressing them. This tiered approach is based on the contact's engagement level.
Technical article
Bloomreach's documentation on email deliverability states that most soft bounces today are caused by sudden increases in email sending volume. This highlights the importance of consistent sending patterns and proper IP warming for senders.
Related resources
8 resources
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