What are the best practices for managing hard and soft bounces in daily email campaigns?
Matthew Whittaker
Co-founder & CTO, Suped
Published 7 May 2025
Updated 16 Aug 2025
8 min read
Managing email bounces is a critical aspect of maintaining a healthy sender reputation and ensuring strong email deliverability, especially for daily email campaigns. When an email bounces, it means it couldn't be delivered to the recipient's inbox. These bounces fall into two main categories: hard bounces and soft bounces, each requiring a different approach to management.
Understanding the nuances of these bounces and implementing effective strategies to handle them can significantly impact your campaign performance. Ignoring bounces, particularly hard bounces, can lead to serious consequences, including lower inbox placement rates and even being added to email blocklists (or blacklists).
For senders running daily email programs, where volume and consistency are key, a proactive and precise bounce management strategy is essential. It's not just about removing bad addresses, but about understanding the underlying reasons for non-delivery and adapting your sending practices accordingly.
Understanding hard and soft bounces
Before diving into management, it's important to differentiate between hard and soft bounces. A hard bounce indicates a permanent delivery failure. This usually happens when an email address is invalid, non-existent, or has been intentionally blocked by the recipient server. Continuing to send to these addresses is detrimental to your sender reputation, as it signals to internet service providers (ISPs) that your list quality is poor, which could lead to your emails being marked as spam or your domain getting added to a blocklist.
Conversely, a soft bounce signifies a temporary delivery issue. Common reasons include a full inbox, a server being temporarily down, or the email message being too large. Unlike hard bounces, soft bounces may resolve themselves over time. However, persistent soft bounces to the same address can also indicate an underlying problem, such as an abandoned mailbox, and should be monitored carefully.
Both types of bounces affect your deliverability metrics, but hard bounces are far more damaging to your sender reputation. A high bounce rate, especially from hard bounces, can trigger spam filters, reduce your inbox placement, and even lead to your IP address or domain being put on a public or private blocklist. Regular monitoring and appropriate action are key to mitigating these risks.
Proactive bounce prevention
The best defense against high bounce rates is a strong offense, meaning implementing proactive measures to prevent bounces from occurring in the first place. List hygiene is paramount. Regularly cleaning your email list to remove inactive or invalid addresses helps reduce hard bounces. This includes implementing a double opt-in process, which requires subscribers to confirm their subscription, ensuring they truly want to receive your emails and minimizing the chance of typos or fake addresses.
Email verification services are invaluable tools for validating email addresses before sending. These services check if an email address is valid and deliverable, significantly reducing the likelihood of hard bounces and protecting your sender reputation. You can also implement sunset policies to regularly remove subscribers who haven't engaged with your emails in a long time, as these addresses are more prone to becoming unresolvable.
Beyond list quality, proper email authentication is non-negotiable. Setting up SPF, DKIM, and DMARC records helps ISPs verify that your emails are legitimately coming from your domain, reducing the chances of them being flagged as spam or rejected outright. Authenticated emails are more likely to reach the inbox, thereby reducing soft bounces caused by strict spam filters.
Best practices for prevention
Double opt-in: Implement a double opt-in process for all new subscribers to confirm their intent and validity.
Strong authentication: Ensure SPF, DKIM, and DMARC are correctly configured.
Reactive bounce management strategies
Once bounces occur, swift and appropriate action is essential. For hard bounces, the rule is simple: remove the email address from your list immediately and permanently. Continuing to send to these invalid addresses will severely damage your sender reputation and increase the likelihood of your emails hitting spam folders or getting your domain blacklisted (or blocklisted). Most email service providers (ESPs) automatically handle this, but it's crucial to verify your suppression lists.
Managing soft bounces requires a more nuanced approach. Since they are often temporary, you might choose to retry sending to these addresses for a limited number of attempts or over a specific period. For daily mailers, I often see rules that mark a soft bounce as a hard bounce if it persists for a certain number of days, say 10 consecutive days. This helps in identifying abandoned mailboxes that are effectively permanent failures.
It's also beneficial to implement a system where any successful delivery or engagement (like an open or click) resets a soft bounce counter. This ensures that active subscribers are not prematurely removed from your list. Regularly monitoring your bounce rates and understanding what constitutes an acceptable bounce rate is crucial for maintaining a healthy sending environment.
Engagement reset: Reset the bounce counter if the subscriber shows any activity.
Advanced bounce handling and ISP nuances
While general rules for hard and soft bounces are a good starting point, the reality of email delivery is far more complex. Bounce codes, often referred to as Delivery Status Notification (DSN) codes, can vary widely across different ISPs and email providers. A single bounce code, like a 5.1.1 (unknown user), might be classified differently depending on the context provided by the receiving server. Some ISPs might provide additional information that changes the interpretation of a seemingly permanent bounce.
It’s a significant challenge to programmatically interpret all possible bounce codes and their subtleties. Many automated rules engines have thousands of entries, and even then, they might not cover every scenario, especially when different providers return different error messages for the same underlying issue. This highlights why a simplistic approach to bounce rules based solely on initial DSN codes can sometimes lead to incorrect suppressions or missed opportunities for delivery.
When managing a daily mailer, it’s not enough to simply look at the main code. Consider the full bounce message and how your email service provider categorizes these. Ideally, your system should be able to process these details to make more informed decisions about whether to retry, suppress, or investigate further. A robust bounce management system understands that context matters more than just the initial DSN code.
Bounce category
Common DSN codes
Action to take
Hard bounce
5.1.1 (unknown user), 5.0.0 (permanent failure)
Remove immediately: These are permanent. Continuing to send harms reputation.
Soft bounce
4.2.2 (mailbox full), 4.4.1 (network error)
Retry or temporarily suppress: Addresses may become deliverable again. Monitor patterns.
Analyze and retry: May indicate content or authentication issues. Resolve before retrying.
Continuous monitoring and adaptation
Regularly reviewing your bounce data is crucial, especially for daily email senders. Look for patterns, such as sudden spikes in bounces to a specific domain or consistent soft bounces from particular segments. This data can provide valuable insights into deliverability issues that may require adjustments to your sending infrastructure, content, or list acquisition methods. Don't be afraid to experiment with your suppression logic for soft bounces, finding the right balance that protects your sender reputation without prematurely removing engaged subscribers.
For daily mailers sending up to five messages a day, maintaining a clean and responsive list is even more critical. Each bounced email, whether hard or persistent soft, contributes to a negative signal to ISPs. By implementing the best practices outlined, you can significantly reduce bounce rates, enhance your sender reputation, and ultimately ensure your daily campaigns reach their intended audience more effectively.
Views from the trenches
Best practices
Always use a double opt-in process to ensure list quality from the start.
Regularly clean your email lists, removing unengaged subscribers and invalid addresses.
Automate the suppression of hard bounces immediately to protect your sender reputation.
Monitor soft bounce patterns and convert persistent soft bounces into hard bounces after a set number of attempts or days.
Ensure your email authentication (SPF, DKIM, DMARC) is correctly configured and monitored.
Segment your list and tailor content to improve engagement and reduce bounces.
Common pitfalls
Ignoring hard bounces or not suppressing them quickly enough, which severely damages sender reputation.
Overly aggressive soft bounce suppression that removes potentially active subscribers.
Not understanding the nuances of bounce codes and relying only on generic classifications.
Sending to old or purchased lists without prior re-engagement or verification.
Failing to monitor bounce rates and other deliverability metrics regularly.
Not classifying bounces by ISP, as different ISPs can interpret codes differently.
Expert tips
If a mailbox has filled and hasn't been cleaned after 10 days, consider the address abandoned.
The precise classification of bounce codes is crucial for deciding future mail actions. The reason for failure is key.
Avoid arbitrarily setting bounce rules; instead, analyze your specific bounce data to identify the root cause of failures.
Be cautious when interpreting bounce codes, as string matching (e.g., 5.7.6 vs. 5.7.606) can lead to incorrect permanent suppressions.
For daily senders, ensure your bounce rules are not too restrictive; a balanced approach is best for long-term engagement.
Continuously review bounce data to inform strategy, rather than relying on rudimentary, inherited policies.
Marketer view
Marketer from Email Geeks says if a mailbox has filled and hasn't been cleaned after 10 days, it should be considered an abandoned address.
2022-06-20 - Email Geeks
Expert view
Expert from Email Geeks says classifying bounces correctly is paramount because the specific reason for email failure dictates what actions should be taken for future messages to that recipient.
