What types of email bounces should be eliminated and which should be monitored?
Michael Ko
Co-founder & CEO, Suped
Published 28 May 2025
Updated 14 Aug 2025
8 min read
Summary
Understanding how to manage email bounces is critical for maintaining healthy sender reputation and maximizing deliverability. There are different types of bounces, and each requires a specific approach: some should be immediately eliminated from your mailing lists, while others can be monitored and potentially resolved. The key is to differentiate between permanent and temporary delivery failures to ensure your email campaigns remain effective and compliant.
Key findings
Hard bounces: These represent permanent delivery failures, such as an invalid or non-existent email address, and should be removed from your lists immediately.
Soft bounces: These are temporary delivery issues, like a full inbox or a server being down, and can often be resolved or re-attempted. They require monitoring, not immediate elimination.
Block bounces: Some email service providers (ESPs) categorize a separate block bounce type, indicating the message was blocked by a spam filter or firewall, which may or may not be temporary.
Context matters: The approach to managing different bounce types is highly subjective and depends on factors like email volume, technical capabilities, and available resources within an organization.
Granularity of data: The level of detail provided in bounce reports can vary significantly between ESPs, affecting your ability to make nuanced decisions.
Key considerations
Develop a policy: It is essential to establish a clear bounce handling policy specific to your organization's needs and capabilities.
Prioritize hard bounces: Always prioritize the immediate removal of hard bounces to protect your sender reputation and avoid being flagged by ISPs.
Monitor soft bounces: Instead of eliminating all soft bounces, monitor them closely. Many ESPs automatically re-attempt delivery for soft bounces.
Analyze causes: For some bounce types, especially those related to networking or misconfiguration, deeper analysis might reveal temporary issues that can be fixed, rather than requiring immediate removal.
Regular list cleaning: Proactive list hygiene, including regular removal of invalid addresses, is key to minimizing bounce rates and improving deliverability, as detailed by Mailmunch.
What email marketers say
Email marketers often grapple with the decision of how aggressively to manage bounced emails. While some advocate for removing all bounces to maintain a clean list, others highlight the potential for lost marketing opportunities and revenue if valid, temporarily unreachable contacts are discarded. The consensus leans towards a nuanced approach that considers both email hygiene and subscriber engagement to decide which bounced emails can be re-engaged or restored.
Key opinions
Avoid blanket removal: Not all bounces should be immediately eliminated; some may represent valuable, albeit temporarily unreachable, subscribers.
Revenue impact: Every bounce unnecessarily removed could be a lost marketing cost and a lost potential opportunity for revenue growth.
Hybrid approach: The best strategy for managing bounces involves combining email hygiene practices with subscriber engagement metrics.
Granular data need: Marketers often receive generic bounce data from their ESPs, making it difficult to differentiate specific bounce classifications beyond basic hard or soft bounces.
Value of restoration: A significant percentage of bounced emails, particularly soft bounces, can be restored if managed correctly, leading to new revenue opportunities.
Key considerations
Implement a soft bounce tolerance: Define a reasonable soft bounce tolerance before suppressing an address, allowing for temporary issues to resolve.
Combine metrics: Use a combination of email hygiene data and content engagement levels to determine the best course of action for bounced email addresses.
Challenge consultants: Question any recommendations to remove all bounces, especially if they do not account for the potential value of reactivating valid contacts.
Understand ESP limitations: Be aware that the depth of bounce classification varies by ESP; some may only provide basic hard vs. soft bounce categories.
Marketer view
Email marketer from Email Geeks discusses the challenge of balancing bounce elimination versus monitoring. They indicate their team is debating whether to remove all bounces or to keep and analyze those related to networking and bad configuration.
20 May 2020 - Email Geeks
Marketer view
Email marketer from Email Geeks observes that their ESP provides only very generic bounce data. They question how many detailed bounce classifications, beyond basic types, are actually reported back by ESPs and whether this granularity depends solely on the ESP's capabilities.
27 May 2020 - Email Geeks
What the experts say
Email deliverability experts emphasize that bounce management policies are highly individualized, depending on an organization's specific context, volume of mail, and technical setup. They generally agree on the core classification of bounces into hard, soft, or block types, but highlight that the depth of data provided by ESPs can vary. Experts caution against universal solutions, advocating for tailored strategies and careful analysis of bounce data to preserve sender reputation and maximize deliverability.
Key opinions
Subjective policies: Bounce handling policies are very subjective and should be tailored to an organization's specific volume, resources, and technical capabilities.
Consultant role: If an organization lacks a defined bounce handling policy, a deliverability consultant can provide valuable assistance in developing one.
ESP classification: ESPs typically report bounces as hard, soft, or block, though some may only use hard or soft classifications.
Data granularity: The level of detail in bounce classifications reported by an ESP depends on its capabilities and sophistication.
Avoid misinterpretation: The intent of bounce classification diagrams is not to advocate for the indiscriminate removal of all bounces, but rather to guide nuanced decision-making.
Key considerations
Custom policy development: Organizations should work with deliverability experts to craft a bounce management strategy that aligns with their specific email program and goals.
Data collection focus: It is crucial to understand how your mail is being sent and how bounce data is collected and processed by your systems or ESP.
SMTP code interpretation: Familiarize yourself with SMTP bounce codes to make informed decisions about suppression, as different codes indicate different issues.
Reputation management: Effective bounce handling is a cornerstone of maintaining a positive sender reputation, a topic frequently discussed on platforms like Spamresource.
Expert view
Deliverability expert from Email Geeks states that bounce handling policies are highly organization-specific and subjective. They depend on numerous factors, including the volume of email sent, available resources, and technical capabilities, necessitating a tailored approach.
20 May 2020 - Email Geeks
Expert view
Deliverability expert from Email Geeks suggests that if an organization lacks a bounce handling policy, it should develop one. They indicate that a consultant can assist with this process, especially if the organization is already referencing a deliverability expert's (Laura's) collateral.
20 May 2020 - Email Geeks
What the documentation says
Technical documentation and industry guides universally distinguish between hard and soft bounces, emphasizing that they require distinct handling. Hard bounces are identified as irreversible delivery failures, mandating immediate removal to protect sender reputation. Soft bounces, conversely, represent temporary conditions and are often subject to multiple re-delivery attempts before an address is eventually suppressed. Documentation also highlights that email providers actively monitor bounce rates, and excessive rates can lead to severe penalties, including suspension of sending privileges or IP/domain blocklisting.
Key findings
Permanent vs. temporary: Hard bounces are permanent, unfixable failures, while soft bounces are temporary delivery impediments.
Immediate suppression: Hard bounces necessitate immediate removal from mailing lists to preserve sender reputation and ensure future deliverability.
Retry attempts: Soft bounces typically trigger multiple re-delivery attempts by ESPs over a period before the address is eventually suppressed, if the issue persists.
High bounce rate risks: High hard bounce rates can lead to email sending suspension and negatively impact sender score, affecting all future campaigns.
Proactive list cleaning: Regularly removing invalid or inactive addresses from your list is crucial for lowering overall bounce rates and enhancing sender reputation.
Key considerations
Automated hard bounce suppression: Ensure your ESP or sending system has automated processes in place to immediately suppress addresses that generate hard bounces.
Soft bounce logic: Understand and configure the soft bounce suppression logic, defining how many retries or how long a temporary failure is tolerated before suppression.
Monitor 4xx errors: While 4xx mail errors are often temporary, persistent 4xx errors should be treated akin to soft bounces that warrant eventual suppression.
ESPs' bounce reports: Regularly review your ESP's bounce reports and documentation to understand their specific bounce classifications and recommended actions, as detailed in the Klaviyo Help Center.
Technical article
Documentation from Guardian Digital states that a hard bounce signifies a permanent delivery failure that cannot be fixed. It advises that little can be done to address such failures, implying these addresses should be removed.
05 Mar 2023 - Guardian Digital
Technical article
Documentation from Twilio advises that hard bounces should be removed from mailing lists immediately to maintain a healthy sender reputation. It contrasts this with soft bounces, which can generally be retried.
