As email marketers, we constantly monitor our campaign performance, and one of the most critical metrics we track is the bounce rate. It tells us how many of our emails aren't making it to the intended inboxes, which can be a red flag for our overall email health. But what exactly are these bounces, and why are we seeing them?
Understanding the different types of bounces is essential for troubleshooting and maintaining a strong sender reputation. Without this insight, it's difficult to diagnose problems, clean our lists effectively, and ultimately, ensure our messages reach their audience.
What are email bounces and why do they happen?
Email bounces fall into two main categories: hard bounces and soft bounces. Each indicates a different underlying issue and requires a distinct approach for handling them.
Hard bounces indicate a permanent delivery failure. This typically means the email address is invalid, the domain name does not exist, or the recipient's server has completely blocked delivery for a specific, unchangeable reason. When we see a hard bounce, it's a clear signal to remove that address from our list immediately. Continuing to send to these addresses hurts our sender reputation significantly. You can read more about hard bounces versus soft bounces to get a better understanding.
Soft bounces, on the other hand, are temporary delivery failures. This could be due to a full inbox, a server being temporarily unavailable, or the message size being too large. While they don't necessitate immediate removal from our list, a high volume of soft bounces can still signal issues with our email practices or the quality of our recipient list. It's crucial to classify and handle these different bounce types to maintain a healthy email program.
Bounce type
Reason
Action required
Hard bounce
Permanent error, e.g., invalid email address, domain not found.
Immediately remove recipient from your list.
Soft bounce
Temporary issue, e.g., full inbox, server downtime, message too large.
Monitor. Retry later. Consider removal if persists over time.
The impact of bounces on your sender reputation
Bounces directly impact our email deliverability and, by extension, our sender reputation. Internet Service Providers (ISPs) and mailbox providers like Gmail and Yahoo use bounce rates as a key indicator of list quality and sending practices. High bounce rates signal that we might be sending to old, invalid, or low-quality addresses, which can lead to our emails being flagged as spam.
If our bounce rates are consistently high, especially hard bounces, ISPs might start to filter our emails more aggressively, sending them straight to the spam folder or even rejecting them entirely. This isn't just about a few emails not getting through, it's about damaging our overall domain and IP reputation, making it harder for all our future campaigns to reach the inbox. You can learn more about how bounces impact deliverability.
The silent threat of email bounces
Even if an email doesn't hard bounce, repeatedly hitting full inboxes or unresponsive servers can flag your sending behavior as suspicious. This can lead to your domain or IP being placed on a blacklist (or blocklist), preventing your emails from reaching recipients even if the addresses are valid. It's important to understand what an email blocklist is and how it works.
A damaged sender reputation is incredibly difficult to repair and can have long-term consequences for our marketing efforts. It's a key reason why we need to proactively manage our bounce rates and regularly clean our email lists. This also applies to soft bounces, as a consistently high soft bounce rate for a particular email address might suggest it's time to remove it, rather than continually trying to deliver messages that won't get through.
What's an acceptable bounce rate?
One of the most common questions we ask ourselves is, "What's a good bounce rate?" While it can vary by industry and list acquisition methods, there are general benchmarks. Many sources, including Mailmunch, suggest that an email bounce rate below 2% is ideal. Anything between 2-5% might warrant investigation, and rates above 5% typically indicate a significant problem that needs urgent attention.
These benchmarks aren't arbitrary, they are derived from aggregate data across millions of email campaigns. They serve as a quick health check for our email program. We should be constantly monitoring our bounce rates to maintain a healthy email reputation.
Good bounce rate
Bounce rate generally 1.5% or below is considered optimal for email marketing, indicating a highly engaged and well-maintained list. This helps ensure high inbox placement rates.
High bounce rate
A bounce rate over 5% or higher signals a significant problem, potentially leading to your IP or domain being blocklisted, causing major deliverability issues. It's crucial to identify the root cause.
It's important to remember that soft bounces count against our overall bounce rate calculation. While a few soft bounces are normal, a persistent increase can still signal issues with list decay or temporary server problems that, if unaddressed, might lead to more permanent blocks. This is why understanding the acceptable bounce rate threshold is critical for our sender reputation.
Practical strategies to reduce bounce rates
Proactively managing bounces is key to successful email marketing. Here are a few strategies that we find effective in reducing bounce rates and improving deliverability:
List hygiene: Regularly clean our email lists by removing inactive subscribers, hard bounces, and any addresses that consistently soft bounce. This ensures we're only sending to engaged recipients.
Email validation: Implement a robust email validation process at the point of signup and periodically for our existing lists. This helps catch invalid addresses before they even enter our system. This is a critical step because typical bounce rates after email validation should be very low.
Authentication standards: Ensure proper implementation of SPF, DKIM, and DMARC. These protocols verify our sending identity, making it less likely that our emails are rejected or marked as spam. For a quick guide on these, check out a simple guide to DMARC, SPF, and DKIM.
Engaging content: Provide valuable and engaging content to reduce spam complaints and encourage interaction, which positively impacts our sender reputation.
We also regularly monitor Google Postmaster Tools and other postmaster feedback loops to identify specific bounce reasons and address them promptly. This data is invaluable for pinpointing deliverability issues and refining our email strategy.
Views from the trenches
Best practices
Maintain a clean email list by regularly removing hard bounces and inactive subscribers.
Implement email validation at the point of signup to prevent invalid addresses from entering your list.
Authenticate your emails using SPF, DKIM, and DMARC to build trust with mailbox providers.
Monitor your bounce rates closely and investigate any sudden spikes or consistent increases.
Common pitfalls
Ignoring hard bounces and continuing to send to invalid email addresses.
Not segmenting your audience, leading to irrelevant content and higher bounce rates.
Failing to implement proper email authentication, which can lead to increased rejections.
Purchasing email lists, which often contain outdated or invalid contacts.
Expert tips
Expert tip: Focus on quality over quantity for your email list. A smaller, engaged list will always outperform a large, uncleaned one.
Expert tip: Understand that some soft bounces are normal, but persistent soft bounces indicate a deeper issue that needs investigation.
Expert tip: Leverage bounce data to refine your audience targeting and content strategy.
Expert tip: Consider a re-engagement campaign for inactive subscribers before removing them entirely.
Expert view
Expert from Email Geeks says they've been seeing an increase in temporary bounces from older, less active domains, likely due to stricter filtering on dormant mailboxes.
2024-01-31 - Email Geeks
Expert view
Expert from Email Geeks says that a common bounce they observe is 'mailbox full', which highlights the importance of re-engagement campaigns and list hygiene.
2024-01-31 - Email Geeks
Maintaining email list health
Bounce rates are more than just a number, they're a vital indicator of our email program's health and our sender reputation. By understanding the different types of bounces, their impact, and what constitutes an acceptable rate, we can take proactive steps to minimize them. Ultimately, this leads to better inbox placement, higher engagement, and more successful marketing campaigns.
Regular list cleaning, robust email validation, and adherence to email authentication standards like SPF, DKIM, and DMARC are non-negotiable for any serious email marketer. By prioritizing these practices, we can ensure our messages reach their intended audience, fostering stronger connections and driving better results.
Gmail and 
Yahoo use bounce rates as a key indicator of list quality and sending practices. High bounce rates signal that we might be sending to old, invalid, or low-quality addresses, which can lead to our emails being flagged as spam.
1.5% or below is considered optimal for email marketing, indicating a highly engaged and well-maintained list. This helps ensure high inbox placement rates.
over 5% or higher signals a significant problem, potentially leading to your IP or domain being blocklisted, causing major deliverability issues. It's crucial to identify the root cause.
