Summary
The consensus is that soft bounces can negatively impact email deliverability and sender reputation, but the extent varies. While not as immediately detrimental as hard bounces, consistently high soft bounce rates can signal underlying issues. The effect depends on factors like the ISP, type of soft bounce (e.g., mailbox full vs. server block), sending frequency, and overall list hygiene. Experts and marketers recommend monitoring bounce rates, investigating patterns, and maintaining a clean email list. Gmail's unique storage quota system can also influence 'mailbox full' bounces.
Key findings
- Variable Impact: The impact of soft bounces depends on the ISP and the specific type of soft bounce.
- Indicator of Problems: High soft bounce rates can indicate issues with list quality (stale, invalid addresses) or sender reputation.
- Cumulative Effect: Repeated soft bounces to the same addresses can harm sender reputation and potentially lead to blacklisting.
- Importance of Monitoring: Monitoring soft bounce rates, analyzing the causes, and proactively managing lists are crucial.
- Gmail's Storage Quota: Gmail's unique storage system can cause 'mailbox full' bounces even when email volume isn't the issue.
Key considerations
- ISP Policies: Be aware of the varying policies and thresholds for soft bounces among different ISPs.
- Bounce Type: Distinguish between different types of soft bounces (e.g., mailbox full, server block) and address them accordingly.
- List Hygiene: Implement a robust list cleaning process to remove inactive or problematic addresses.
- ESP Handling: Understand how your ESP handles soft bounces and what actions they take (e.g., suppression).
- Proactive Management: Don't ignore soft bounces; investigate patterns and take corrective action to maintain deliverability.
What email marketers say
14 marketer opinions
The impact of soft bounces on email deliverability and sender reputation is nuanced. While not as immediately damaging as hard bounces, consistently high soft bounce rates can negatively affect deliverability. The effect depends on several factors including the ISP, the type of soft bounce, the frequency of sending, and overall list hygiene. Some soft bounces, like those due to weak sender reputation or server blocks, are more concerning. Regular list cleaning, monitoring bounce rates, and understanding your ESP's bounce handling policies are crucial for maintaining good deliverability.
Key opinions
- Variable Impact: Soft bounces don't always have a direct negative impact; their effect varies based on the cause and the ISP's policies.
- Indicator of Issues: High soft bounce rates can indicate problems with list quality, such as stale or invalid addresses.
- Reputation Damage: Repeatedly sending to addresses that soft bounce can indirectly harm your sender reputation.
- Importance of Monitoring: Monitoring soft bounce rates and understanding the reasons behind them is crucial for maintaining deliverability.
- Proactive List Management: Regularly cleaning your email list and removing inactive or problematic addresses is essential to prevent deliverability issues.
Key considerations
- ISP Specifics: Different ISPs have different thresholds and policies regarding soft bounces; what is acceptable for one may not be for another.
- Type of Soft Bounce: Differentiate between types of soft bounces (e.g., mailbox full vs. server block) as they have different implications.
- ESP Handling: Understand how your ESP handles soft bounces, including suppression policies and reporting.
- List Hygiene: Implement regular list cleaning practices to remove inactive or problematic addresses.
- Monitoring and Analysis: Continuously monitor bounce rates, analyze the causes of soft bounces, and adjust sending practices accordingly.
Marketer view
Marketer from Email Geeks explains that whether soft bounces impact deliverability depends on the ISP and the type of soft bounce. High soft bounce rates (above 2%) are a bad sign, but otherwise, other metrics are more important for assessing reputation with major ISPs.
19 Jan 2022 - Email Geeks
Marketer view
Email marketer from Reddit shares that if you see lots of soft bounces, it's a sign that your list might be getting old or has a lot of invalid addresses. Cleaning your list regularly can prevent deliverability issues.
13 Feb 2024 - Reddit
What the experts say
3 expert opinions
Experts agree that the impact of soft bounces on deliverability is complex. It is not a simple yes or no answer. Gmail's storage quotas include all data, potentially leading to 'mailbox full' soft bounces unrelated to email volume. The impact depends on the specific bounce code, server policies, and sender reputation. Although temporary failures are not as severe as hard bounces, frequent occurrences should be monitored as they may signal deliverability issues.
Key opinions
- Context Matters: The effect of soft bounces depends on factors beyond simple delivery failure.
- Gmail Quota: Gmail's storage system, which encompasses all data, influences 'mailbox full' bounces.
- Monitoring Still Important: Frequent soft bounces, while temporary, can signal larger deliverability issues and should be monitored.
Key considerations
- Bounce Code Analysis: Examine specific bounce codes to understand the underlying reason for the soft bounce.
- Server Policies: Consider the policies of the receiving mail server, as they vary.
- Sender Reputation: Understand how soft bounces may impact your sender reputation and take steps to maintain a positive reputation.
- Monitor trends: Be aware that frequent soft bounces can signal deliverability problems
Expert view
Expert from Email Geeks reminds that Gmail counts everything (pictures, videos) towards the storage quota, potentially causing 'mailbox full' errors. Gmail signals this using both 4xy and 5xy codes.
21 Mar 2023 - Email Geeks
Expert view
Expert from Word to the Wise explains that there's no simple 'yes' or 'no' answer. It depends on the specific bounce code, the receiving mail server's policies, and your overall sending reputation. Repeated soft bounces to the same address can be a negative signal.
3 Jun 2025 - Word to the Wise
What the documentation says
5 technical articles
Email marketing documentation generally indicates that soft bounces, while not immediately as damaging as hard bounces, can negatively impact email deliverability and sender reputation. While some platforms suggest soft bounces aren't dangerous until they become hard bounces, others emphasize that any bounce affects deliverability, leading to profile suppression or being seen as an unreliable sender. A pattern of soft bounces should be investigated, and those addresses removed from the list.
Key findings
- Deliverability Impact: Soft bounces can affect deliverability, even if the impact isn't immediate.
- Cumulative Effect: Consistently high soft bounce rates can lead ISPs to view senders as unreliable.
- Platform Action: Some platforms automatically suppress profiles after a certain number of consecutive soft bounces.
- Investigation Needed: A pattern of soft bounces to the same addresses warrants investigation.
- List Management: Unresponsive addresses should be removed from email lists.
Key considerations
- Frequency Matters: Consider the frequency and consistency of soft bounces to particular email addresses.
- Platform Policies: Understand your email marketing platform's policies regarding soft bounces and suppression.
- Proactive Monitoring: Monitor soft bounce rates to identify potential problems early.
- Data Hygiene: Remove persistently bouncing addresses from your email lists to maintain a good sender reputation.
Technical article
Documentation from SendGrid Docs shares that while soft bounces might not immediately damage your sender reputation, consistently high soft bounce rates can lead ISPs to view you as an unreliable sender, negatively impacting deliverability over time.
23 Jan 2023 - SendGrid Docs
Technical article
Documentation from SparkPost Documentation indicates that while soft bounces are temporary, a pattern of soft bounces to the same addresses should be investigated and those addresses should be removed from the list after a certain number of attempts.
31 Dec 2023 - SparkPost Documentation
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