Should I suppress soft bounces from my email lists for better list hygiene?
Matthew Whittaker
Co-founder & CTO, Suped
Published 10 May 2025
Updated 17 Aug 2025
7 min read
Managing email bounces is a critical aspect of maintaining a healthy sender reputation and achieving strong email deliverability. While hard bounces clearly signal permanent delivery failures that require immediate removal from your lists, the situation with soft bounces is often more nuanced.
The question of whether to suppress soft bounces for better list hygiene is not always straightforward. Soft bounces indicate temporary issues, such as a full mailbox or a server being temporarily unavailable. These temporary conditions mean the recipient's email address is still valid, and future delivery attempts might succeed.
However, ignoring persistent soft bounces can negatively impact your sender reputation and campaign performance. Finding the right balance between patience and proactive list cleaning is key to optimizing your email program.
Understanding email bounces
Before deciding on a suppression strategy, it is essential to understand what constitutes a soft bounce versus a hard bounce. A hard bounce occurs when an email is permanently undeliverable, typically because the email address is invalid or no longer exists. These should be removed from your list immediately to protect your sender reputation. For more details, consider our guide on how hard and soft bounces are defined.
In contrast, a soft bounce indicates a temporary delivery issue. Common reasons include the recipient's mailbox being full, the server being temporarily unavailable, or the message size exceeding the recipient's limit. Your Email Service Provider (ESP) will typically retry sending emails that result in a soft bounce over a period of time before classifying them as a hard bounce or suppressing them.
It is important to note that the terms 'soft' and 'hard' bounces are largely conventions, and the actual classification by ESPs can vary based on the specific SMTP bounce codes received. Focusing on these underlying codes can provide a more accurate picture of the problem. You can learn more about which SMTP bounce codes should lead to suppression.
Why soft bounces are tricky
One of the most significant challenges with soft bounces is that they are not always purely temporary. Some Internet Service Providers (ISPs) or Mailbox Providers (MBPs), like Yahoo, may issue a soft bounce for reasons related to sender reputation or rate limiting, even if the address is valid. If you automatically suppress all soft bounces without understanding the underlying cause, you risk removing legitimate subscribers from your list.
This scenario highlights why a blanket suppression policy for soft bounces can be detrimental. For example, if your sending volume suddenly increases, an ISP might temporarily throttle your emails, leading to soft bounces. These are valid addresses that are merely being delayed, not permanently undeliverable. Removing them could significantly shrink your effective audience.
The complexity of bounce handling means that a simple 'soft bounce' label can be misleading. As explained by Word to the Wise, understanding the precise bounce reason is far more valuable than relying on generic classifications. This requires deeper analysis of SMTP response codes and not just the high-level bounce categories.
The risk of aggressive suppression
Suppressing soft bounces too quickly can lead to a significant loss of valid subscribers, especially when the bounces are due to temporary issues like rate limiting or a full mailbox that resolves quickly. This can undermine the growth of your list and reduce your reach. It is always better to understand the best practice for determining how many soft bounces before suppressing a user.
Impact on sender reputation and deliverability
While soft bounces are temporary, repeated soft bounces from the same address can signal a deeper problem and negatively affect your sender reputation. ISPs monitor bounce rates closely, and a consistently high soft bounce rate can indicate an unhealthy list or problematic sending practices. This can lead to your emails being flagged as spam, or even result in your domain or IP being added to a blocklist (or blacklist).
Maintaining good email list hygiene is crucial for overall email deliverability. High bounce rates of any kind can signal to mailbox providers that your emails are not desired or are being sent to invalid addresses, which diminishes your sender score. This is why it's important to understand if soft bounces affect email deliverability.
While most ESPs automatically handle hard bounces, the management of soft bounces often requires a more strategic approach tailored to the specific bounce reason and the subscriber's engagement history. Ignoring these persistent issues can impact how bounces impact email deliverability.
Short-term soft bounce
Causes: Temporary server issues, recipient mailbox full (briefly), message too large for inbox.
Impact: Minimal impact on sender reputation if infrequent. ESPs typically retry automatically.
Action: Monitor and allow ESP to retry. No immediate suppression needed.
Persistent soft bounce
Causes: Mailbox consistently full or abandoned, recurring server issues at recipient's end, reputation-based throttling (e.g., from Yahoo).
Impact: Can harm sender reputation, increase bounce rates, and lead to blocklisting if not addressed.
Action: Investigate underlying reason. Consider temporary suppression or removal after multiple consecutive bounces. Review your blocklist monitoring for signs of issues.
Strategies for managing soft bounces
Most robust ESPs, like Pardot, have sophisticated built-in mechanisms for managing soft bounces. They will typically attempt to resend the email several times over a period before deciding to suppress the address. This default behavior is often sufficient for most senders, as it allows temporary issues to resolve without manual intervention.
However, for advanced users or those experiencing specific deliverability challenges, customizing your soft bounce handling can be beneficial. This might involve temporarily holding out soft bounces from mailings for a week or two, then re-engaging them. If they continue to soft bounce after multiple attempts and across various campaigns, it might be time to consider suppressing them to protect your list's integrity. Learn more about the recommended soft bounce suppression logic.
Another strategy is to combine bounce data with engagement metrics. If an address consistently soft bounces and has also shown no engagement (opens or clicks) over a long period, it's more likely to be an abandoned account rather than a temporary glitch. In such cases, removing the address can improve your overall engagement rates and reduce unnecessary sending to dormant contacts. This ensures you are not emailing addresses that keep soft bouncing.
Bounce reason
SMTP code category
Recommended action
Mailbox full
4.2.2
Retries are usually effective. If persistent over several sends, consider temporary suppression or re-engagement campaigns.
Server temporarily unavailable
4.x.x
Rely on ESP retries. These are often transient network issues.
Message too large
5.3.4
Reduce email size, or suppress if this is a recurring issue for a specific recipient.
Reputation/throttling
4.7.x
Review sender reputation and sending practices. Do not suppress immediately, as addresses are often valid. Consider our advice on what types of email bounces to monitor.
Views from the trenches
Best practices
Regularly analyze SMTP bounce codes to understand the root cause of non-delivery.
Implement a retry logic that differentiates between temporary and persistent issues before considering suppression.
Segment your audience based on engagement levels to identify which soft bounces are less likely to recover.
Common pitfalls
Relying solely on generic 'soft bounce' labels without understanding the specific bounce reasons.
Aggressively suppressing soft bounces too quickly, leading to the removal of valid subscribers.
Not distinguishing between consecutive soft bounces and total lifetime soft bounces for an address.
Expert tips
Understand your ESP's specific bounce handling logic and reporting, as it can vary widely.
Prioritize hard bounce suppression immediately, but approach soft bounces with a more nuanced, strategic retry approach.
For reputation-based soft bounces, focus on improving overall sender reputation rather than suppressing individual addresses.
Expert view
Expert from Email Geeks says that 'soft' and 'hard' bounces are often conceptual terms, and the true reason for a bounce depends on the specific SMTP response code, not a general label.
2024-10-30 - Email Geeks
Marketer view
Marketer from Email Geeks says they convert soft bounces into hard bounces after three consecutive email sends, as analysis showed these typically resulted in no interaction.
2024-10-30 - Email Geeks
A balanced approach to soft bounces
The decision to suppress soft bounces is not a one-size-fits-all answer. While hard bounces should be dealt with immediately, soft bounces require a more thoughtful approach. Over-aggressive suppression can lead to the loss of valid subscribers, while under-managing them can harm your sender reputation and deliverability.
The best practice involves understanding the true nature of the bounce (via SMTP codes), leveraging your ESP's retry mechanisms, and analyzing engagement alongside bounce data. This nuanced strategy ensures you maintain a clean, high-performing email list without sacrificing valuable contacts.
By adopting a data-driven approach, you can effectively manage soft bounces, improve your list hygiene, and enhance your overall email deliverability, ensuring your messages reach the inbox consistently.
Yahoo).
Pardot, have sophisticated built-in mechanisms for managing soft bounces. They will typically attempt to resend the email several times over a period before deciding to suppress the address. This default behavior is often sufficient for most senders, as it allows temporary issues to resolve without manual intervention.
