How to troubleshoot high soft bounce rates and poor inbox placement?
Michael Ko
Co-founder & CEO, Suped
Published 29 Jul 2025
Updated 14 Aug 2025
9 min read
Summary
High soft bounce rates and poor inbox placement often indicate underlying issues with sender reputation, list hygiene, or content quality. While soft bounces are temporary delivery failures, a consistent pattern across multiple mailbox providers (MBPs) suggests a deeper problem that requires careful investigation. Understanding the specific bounce codes and reasons is paramount, as is assessing the health of your email list, especially after re-engagement campaigns targeting older segments. Addressing these issues can help restore your email deliverability and ensure your messages reach the inbox.
Key findings
Data importance: Lack of detailed soft bounce data from your Email Service Provider (ESP) significantly hinders effective troubleshooting.
Cross-provider issues: Observing high soft bounces across major providers (e.g., Gmail, Yahoo, Hotmail) often points to a systemic issue rather than isolated incidents.
List quality: Old, unengaged, or unvetted email list segments, particularly those used in re-engagement campaigns, are a common cause of increased soft bounces and declining inbox placement. This can also lead to issues like over-quota mailboxes.
Sender reputation: A sudden surge in volume to dormant lists can severely damage your sender reputation, affecting even subsequent sends to engaged users. Improving your domain reputation is critical.
Blacklist status: While not always the cause of soft bounces, being listed on major blocklists (or blacklists) like Spamhaus can lead to widespread rejection or deferral of emails, impacting inbox placement significantly.
Key considerations
Obtain detailed bounce reports: Work with your ESP to get specific soft bounce codes and reasons, as this data is crucial for accurate diagnosis and resolution. This is often available in email bounce rate reports.
Inspect email content and links: Ensure no linked content is compromised or flagged for phishing, as this can trigger immediate soft bounces or spam filtering.
Segment your audience strategically: Avoid sending large volumes to inactive or old segments without prior re-engagement strategies and list cleaning. Consider running these lists through a validation service.
Monitor blocklist status: Regularly check if your domain or sending IP is listed on any major blocklists. If listed, understand the reason and follow the delisting procedures. Our guide to email blocklists can provide more information.
Manage mail queues: If applicable, ensure your mail queues are flushed to remove problematic emails that could be continually impacting your reputation through retry attempts.
Allow for reputation recovery: If your reputation has been severely impacted, consider a temporary pause or significant reduction in sending volume to allow your sender score to recover.
What email marketers say
Email marketers grappling with high soft bounce rates often find themselves in a challenging position, particularly when comprehensive bounce data is unavailable. A common thread among their experiences is the impact of re-engagement campaigns targeting older, less active segments. While the intention behind these campaigns is often good, they can inadvertently trigger widespread soft bounces and diminish inbox placement across major providers, even if initial checks for blacklisting come up empty. The consensus is that detailed bounce data and rigorous list hygiene are critical to unraveling and resolving these issues.
Key opinions
Data is key: Marketers frequently express frustration when their ESP does not provide specific soft bounce types, highlighting this as a major barrier to effective troubleshooting.
Re-engagement risks: Launching large campaigns to older or unengaged user segments is consistently identified as a primary trigger for high soft bounce rates and subsequent poor inbox placement.
Persistent problems: Even after reducing send volumes or targeting more engaged users, the negative effects (such as poor placement) from a previous problematic send can linger.
Blacklist checks: Many marketers check common blacklists first, but note that their domain or IP might not appear on these, even with significant deliverability issues.
Key considerations
Prioritize data access: Insist on obtaining granular soft bounce data from your ESP. This information is indispensable for pinpointing the exact reasons for delivery failures.
Proactive list hygiene: Before any re-engagement campaign, especially one targeting dormant users, run the segment through an email validation service. This helps prevent hitting abandoned addresses or spam traps.
Understand provider nuances: Be aware that providers like Yahoo and Hotmail may implement rate limiting if they detect poor engagement or sudden, large sends to less responsive users. This can lead to soft bounces, as detailed by Mailgun.
Long-term impact: Recognize that a single problematic send can have a lasting negative impact on your sender reputation and subsequent inbox placement, even for well-performing segments. Consistent list maintenance and monitoring are key.
Marketer view
Marketer from Email Geeks notes that they are observing soft bounces across major providers like Yahoo, Gmail, and Hotmail but lack specific bounce types from their ESP. This makes troubleshooting difficult because the underlying causes are not clear.
10 Oct 2019 - Email Geeks
Marketer view
Email marketer from Quora suggests that for iCloud recipients, receiving "user is overquota" soft bounce messages indicates a full inbox, which is a common temporary issue but can be indicative of inactive users if persistent. This highlights the need to monitor these types of bounces as they can also suggest old or unengaged contacts.
15 Jan 2024 - Quora
What the experts say
Email deliverability experts highlight that high soft bounce rates across multiple providers signal deep-seated problems, often related to compromised links, poor list data, or domain blocklisting. They stress that a sudden increase in mailing volume to dormant addresses can be perceived as spamming, severely damaging sender reputation. Crucially, they advise obtaining granular bounce data to properly diagnose issues and, if necessary, pausing sends to allow reputation to recover. The general consensus is that proactive data management and understanding bounce types are fundamental to maintaining good inbox placement.
Key opinions
Holistic view needed: Resolution of soft bounce issues requires a comprehensive understanding of the 'who, what, when, and where' of the problem.
Core issues: Top suspects for widespread soft bounces include compromised links (phishing), sending to bad/old/unvetted data, and domain listings on major blocklists.
Overquota signals: An increase in 'user is overquota' bounces strongly points to issues with list quality, specifically targeting abandoned or rarely used email addresses.
Queue impact: Soft bounces lead to emails being queued and retried; if problematic data remains in queues, it can continue to negatively affect deliverability.
Reputation damage: Severe reputation damage from a large problematic send may require a temporary cessation of mailing to allow the sender's reputation to recover. This impacts how long it takes to recover domain reputation.
Key considerations
Data granularity: Always strive for the most detailed bounce data possible from your ESP, as it provides specific insights into the cause of failures.
Link verification: Regularly check all URLs within your emails for signs of compromise or malicious flags that could lead to bounces or spam classification. This is part of a broader strategy for diagnosing email deliverability issues.
Aggressive list cleaning: Be proactive in removing old, unengaged, or unverified contacts from your active sending lists to avoid hitting spam traps or abandoned mailboxes. This is particularly important for effective list hygiene.
Blocklist monitoring: Implement robust blocklist monitoring for both your domain and sending IPs, as listing on a significant blocklist can immediately impact deliverability.
Expert view
Expert from Email Geeks emphasizes that troubleshooting email delivery issues requires understanding the full context, including who, what, when, and where the problems occur. Without this comprehensive view, diagnosis can be incomplete and solutions ineffective.
10 Oct 2019 - Email Geeks
Expert view
Expert from Word to the Wise advises that an effective deliverability strategy includes regular monitoring of email engagement metrics. This proactive approach helps identify declining engagement trends that could lead to soft bounces and poor inbox placement before they become critical issues.
22 Apr 2024 - Word to the Wise
What the documentation says
Official documentation and industry reports consistently emphasize that email deliverability is a complex interplay of sender reputation, email authentication, and list quality. High soft bounce rates are often symptoms of poor list hygiene or a declining sender reputation, which can be exacerbated by sudden changes in sending behavior or the presence of unengaged recipients. Mailbox providers use various signals to determine inbox placement, including engagement metrics and adherence to authentication standards. Resolving these issues requires a proactive approach to list management and adherence to best practices.
Key findings
List hygiene is paramount: Maintaining a clean and engaged email list is repeatedly cited as the most effective way to reduce bounce rates and improve inbox placement.
Authentication importance: Properly configured email authentication (SPF, DKIM, DMARC) is essential for proving sender legitimacy and preventing emails from being flagged as spam or bouncing. Our guide on DMARC, SPF, and DKIM explains more.
Engagement impact: High engagement (opens, clicks) signals positive sender reputation, while low engagement can lead to soft bounces and spam folder placement.
Bounce rate thresholds: Many sources suggest keeping overall bounce rates, including soft bounces, below 2% to maintain a healthy sender reputation.
Key considerations
Regular list cleaning: Implement automated processes to remove bounced addresses, especially hard bounces, and periodically re-validate older segments. This helps to resolve bounce issues effectively.
Monitor engagement metrics: Track open rates, click-through rates, and spam complaint rates closely. Declining engagement is a strong indicator of potential deliverability problems.
Ensure proper authentication: Verify that your SPF, DKIM, and DMARC records are correctly set up and passing authentication tests. Authentication failures can significantly contribute to soft bounces and poor inbox placement, causing emails to go to spam. See our list of DMARC tags for more information.
Segment non-engagers: Create specific segments for unengaged users and consider re-engagement strategies (or removal) to avoid negatively impacting your overall sender reputation.
Technical article
Mailgun documentation explains that soft bounces occur due to temporary issues, such as a recipient's inbox being full or the mail server being unavailable. It also highlights that persistent soft bounces can still negatively affect deliverability over time, requiring senders to investigate and resolve underlying issues to maintain good sender reputation.
05 Nov 2023 - Mailgun
Technical article
Klaviyo Help Center documentation states that having all necessary DNS records in place, including SPF, DKIM, and DMARC, is crucial for resolving bounce issues. Proper email authentication helps mailbox providers verify the sender's legitimacy, which significantly improves deliverability and reduces the likelihood of emails bouncing or landing in spam.
