How do bounces impact email deliverability and how can I minimize them?
Michael Ko
Co-founder & CEO, Suped
Published 25 Apr 2025
Updated 19 Aug 2025
7 min read
Email bounces are a common occurrence for any sender, but their impact on email deliverability and sender reputation can be significant. When an email bounces, it means it couldn't be delivered to the recipient's inbox, and the sending server receives a notification detailing the reason for the failure. Ignoring these signals can lead to severe consequences for your email program.
Understanding the types of bounces and their underlying causes is the first step toward maintaining a healthy email sending infrastructure. Both temporary and permanent delivery failures communicate crucial information to Internet Service Providers (ISPs) and Email Service Providers (ESPs) about the quality of your mailing list and your sending practices.
My goal is to walk through what email bounces are, how they affect your ability to reach the inbox, and crucially, how you can minimize them to safeguard your sender reputation and maximize the effectiveness of your email campaigns.
Understanding email bounces
Email bounces fall into two primary categories: hard bounces and soft bounces. Each type indicates a different kind of delivery failure and carries varying implications for your email program.
A hard bounce signifies a permanent delivery failure. This typically occurs when an email address does not exist, the domain name is invalid, or the recipient's mail server has completely blocked delivery. When an email hard bounces, it means there's no chance for future delivery to that address. Continuing to send emails to hard-bounced addresses is a clear red flag to ISPs and ESPs, indicating poor list hygiene and potentially irresponsible sending practices. Repeated hard bounces can severely damage your sender reputation and overall email deliverability.
Soft bounces, on the other hand, indicate a temporary delivery failure. Common reasons for soft bounces include a full mailbox, the recipient's server being temporarily unavailable, or the email message being too large. While these are usually transient issues, consistent soft bounces to the same address over time can also signal problems, such as an inactive account or a consistently overloaded server. Most email platforms will attempt to resend soft-bounced emails for a certain period, but if the issue persists, the soft bounce may eventually convert into a hard bounce.
Each bounce comes with an SMTP code, which provides specific details about the reason for the non-delivery. Understanding these SMTP bounce codes is crucial for diagnosing and addressing underlying deliverability issues.
Hard bounces
Nature: Permanent delivery failure.
Causes: Non-existent email address, invalid domain, recipient server blocking delivery.
Action: Immediately remove the address from your list.
Soft bounces
Nature: Temporary delivery failure.
Causes: Full mailbox, server unavailable, message too large.
Action: Monitor. If persistent, remove or investigate. Over-quota mailboxes need close attention.
How bounces impact sender reputation
High bounce rates have a direct and detrimental impact on your sender reputation. ISPs and ESPs, such as Google and Yahoo, closely monitor your bounce rate as a key indicator of your sending quality. A consistently high bounce rate suggests that you are sending to outdated or invalid email addresses, which can be interpreted as spam-like behavior. This can lead to your emails being flagged as suspicious, routed to the spam folder, or even rejected outright.
The threshold for an acceptable bounce rate is generally quite low, with most experts recommending keeping it below 2%. Exceeding this benchmark, especially with hard bounces, can significantly diminish your sender reputation, making it harder for your legitimate emails to reach the inbox. This directly impacts your email deliverability, leading to lower engagement rates and reduced ROI from your email marketing efforts. Your IP address or domain might even end up on an email blacklist (or blocklist).
Even soft bounces, if persistent, can contribute to a decline in deliverability. While a single soft bounce might not immediately harm your reputation, a pattern of continuous soft bounces to the same addresses indicates a lack of engagement or an issue with the recipient's server that you need to address. Mailbox providers interpret a high volume of any type of bounce as a sign of a poorly managed or low-quality email list, which can lead to stricter filtering for all your outgoing mail.
This also impacts your ability to recover from deliverability issues. For example, if you're experiencing a sudden spike in bounce rates, it could indicate that you're hitting spam traps or that your list contains a significant number of inactive or invalid addresses, hindering your domain reputation recovery.
Strategies to minimize email bounces
Minimizing email bounces requires a proactive approach, focusing on list quality and proper email sending practices. Here are some key strategies I recommend implementing.
First, implement a confirmed opt-in or double opt-in process for all new subscribers. This ensures that every email address added to your list is not only valid but also that the owner genuinely wishes to receive your emails. It significantly reduces the chance of adding invalid or mistyped addresses. As an added benefit, it cultivates a more engaged audience, which further boosts your email deliverability by improving engagement metrics.
Regularly clean your email list. This involves removing inactive subscribers, hard-bounced addresses, and addresses that consistently soft bounce. Many ESPs automatically handle hard bounces, but it's important to monitor and remove these contacts manually if your platform doesn't. Consider using an email validation service to pre-emptively identify and remove invalid addresses before you even send to them. A clean list ensures your emails are sent only to active, interested recipients, which is a cornerstone of good email hygiene.
Finally, ensure your email authentication protocols—SPF, DKIM, and DMARC—are correctly configured. These protocols verify your identity as a legitimate sender and help prevent spoofing and phishing attempts. ISPs are more likely to deliver emails from authenticated senders, reducing the likelihood of your emails being flagged as suspicious and bouncing. You can use a DMARC record generator to get started with DMARC or explore our guides on DMARC, SPF, and DKIM to ensure proper setup.
Views from the trenches
Implementing a robust email deliverability strategy is crucial to minimizing bounces and protecting your sender reputation. Here's a quick reference for best practices and common pitfalls to avoid.
Best practices
Always use a double opt-in process to verify email addresses and confirm subscriber intent.
Regularly clean your email lists by removing hard bounces, unengaged subscribers, and suspicious addresses.
Utilize email validation services before sending to new lists or segments to pre-emptively catch invalid emails.
Monitor your bounce rates closely and investigate the root causes of soft bounces to improve deliverability.
Ensure SPF, DKIM, and DMARC records are correctly configured to authenticate your sending domain and improve trust.
Common pitfalls
Purchasing or scraping email lists, which often contain high numbers of invalid addresses and spam traps.
Ignoring bounce notifications, leading to a build-up of bad addresses and a damaged sender reputation.
Not segmenting your audience, resulting in irrelevant content that increases spam complaints and bounces.
Failing to implement proper email authentication, making your emails more likely to be filtered or bounced by ISPs.
Sending emails with generic or spammy content that triggers spam filters and increases bounce rates.
Expert tips
If domains don't exist, your mail might not even leave your MTA, indicating a deeper problem with address collection.
Monitor your bounce messages and SMTP error codes to understand why emails are failing and troubleshoot effectively.
Focus on the quality of your list acquisition. If many typos or non-existent domains are getting on your list, review your signup process.
While soft bounces may not immediately affect reputation, persistent soft bounces to the same address can eventually lead to negative impacts.
Keep your overall bounce rate below 2% to maintain a healthy sender reputation and avoid deliverability issues.
Expert view
Expert from Email Geeks says that confirmed opt-in methods are crucial for minimizing bounces, ensuring you only have valid and willing addresses on your list.
2021-02-23 - Email Geeks
Expert view
Expert from Email Geeks says that anything under approximately a 2% bounce rate will have minimal impact on deliverability, provided that mail is properly handled and addresses are collected in a way that minimizes non-deliverable entries.
2021-02-23 - Email Geeks
Continuously high bounce rates signal to mailbox providers that you might be engaging in questionable sending practices, such as sending to purchased lists or outdated contacts. This can trigger spam filters, reduce your sending quotas, and land your domain or IP on a blocklist (or blacklist). Maintaining a low bounce rate is a fundamental aspect of effective email deliverability and ensuring your messages reach their intended recipients.
Ensuring email success
Email bounces are more than just failed deliveries, they are critical indicators of your email program's health. By understanding the difference between hard and soft bounces, proactively maintaining a clean email list, and ensuring proper authentication, you can significantly minimize their negative impact. Prioritizing these practices will protect your sender reputation, improve your inbox placement, and ultimately enhance the success of your email campaigns.
Google and 
Yahoo, closely monitor your bounce rate as a key indicator of your sending quality. A consistently high bounce rate suggests that you are sending to outdated or invalid email addresses, which can be interpreted as spam-like behavior. This can lead to your emails being flagged as suspicious, routed to the spam folder, or even rejected outright.
