A bounced email isn’t just a message that didn’t go through—it’s a missed chance to connect. Maybe a subscriber never saw your flash sale, a lead missed your webinar invite, or a loyal customer didn’t get their reward points.
When emails bounce, they don’t reach the people who need them. And if it happens too often, email service providers might think your messages aren’t trustworthy. That means more of your emails could end up in spam folders or even get blocked completely.
The good news? You can fix most bounce issues before they cause problems. Let’s look at why emails bounce and how you can ensure your marketing messages reach their target destination.
Understanding bounced emails
When you send an email, you expect it to land in the recipient’s inbox. But sometimes it doesn’t. Instead, it bounces back, meaning it never got delivered. This is known as a bounced email.
Why does this happen? It could be something simple, like the recipient’s email server having a temporary glitch. Or, it could be a more serious problem, like the entire domain shutting down.
Bounced emails typically fall into 2 main categories:
- Soft bounces are temporary setbacks. The email might still go through later or need a minor fix on your end.
- Hard bounces are permanent roadblocks, letting you know the email will never get delivered to that address.
Knowing the difference between these soft and hard bounce types helps you respond appropriately, whether that means removing addresses from your email list or simply trying again later. The better you manage bounces, the more successful your email campaigns will be.
When too many emails bounce, it doesn’t just mean those particular messages failed to reach their targets. High bounce rates can have a profound ripple effect across your email marketing program.
Email service providers like Gmail, Yahoo, and Outlook constantly monitor sender behavior to protect users from spam. They track metrics including—you guessed it—bounce rates. If they notice a pattern of high bounces from your domain, they may view you as a potentially problematic sender.
This negative sender reputation triggers a cascade of deliverability issues. Your emails might land in spam folders instead of inboxes or get blocked entirely. Some email providers may even suspend or terminate accounts with consistently high bounce rates.
The damage extends beyond just email performance. High bounce rates often signal poor email list-building practices, affecting your overall marketing effectiveness. They also waste resources because you’re paying to send emails that never reach their destination.
Where to find email bounce notifications
When an email bounces, it’s essential to know where to look for the details so you can address the issue. Here are the 3 main places to find bounce error messages.
Email marketing platform dashboard
Most email marketing tools have a dedicated section in your campaign reports for bounce messages. Look for tabs or filters labeled Bounces, Delivery Issues, or Non-Delivered Emails. The platform will likely categorize bounces as soft or hard and provide details like the affected email addresses and reason for the bounce.
Bounce notification emails
You might receive an automatic bounce notification if you send emails through your domain (e.g., Gmail, Outlook, or a business email). These full bounce response messages usually come from “MAILER-DAEMON” or “Postmaster” and include details about why the email didn’t get delivered.
Simple Mail Transfer Protocol (SMTP) error codes
You can check email headers for more technical details if your email service provider doesn’t provide a clear soft or hard bounce message. You can usually view these headers by clicking Show original or View source in your email client. Look for lines containing status= followed by a code.
SMTP codes starting with a 4 (like 4.2.2 for full mailbox) are typically for soft bounces that might succeed later. But if the code begins with 5 (like 5.1.1 for a nonexistent address), it’s likely a hard bounce that won’t resolve with retries.
Soft bounce errors and solutions
Don’t dismiss soft bounces just because they’re temporary problems. These delivery hiccups can hurt your sender reputation when they pile up over time. Here’s how to handle the most common soft bounce issues.
Mailbox full
When you see this soft bounce error, it means the recipient can’t receive new messages because they’ve reached their storage limit. Try sending the email again in a few days, as the recipient may have cleared some space. But if you keep getting this bounce code, it’s probably an inactive account you should remove from your list.
Message too large
Email providers limit the size of messages they’ll accept, with Gmail addresses capping at 25MB and Outlook at 20MB. If your email exceeds these limits, it will bounce back. To solve this soft bounce issue, reduce your file sizes, compress images, or host larger files externally.
Temporary mail server issues
Sometimes, soft bounces occur because the recipient’s server is temporarily down or overloaded. Your email platform will usually try resending your message automatically over the next few days. If the issue persists for longer than 72 hours, you might want to contact the recipient through another channel.
Spam filter block
Your email might bounce if the receiving server’s spam filters flag your content as suspicious. Your message might contain trigger words like free or earn $. Or, you might be using too many exclamation points or all caps in your content. Most email service providers are also wary of attachments, URL shorteners, and suspicious links. And don’t forget, your emails might also bounce back if enough recipients submit spam complaints manually.
Hard bounce errors and solutions
Hard bounces mean your email hit a dead end. Unlike soft bounces, these won’t fix themselves, and continuing to send to these addresses can quickly damage your sender reputation. Let’s explore what causes these permanent failures and how to address them.
Invalid address
Your message has nowhere to go when an email address doesn’t exist. This happens when the recipient has mistyped their email, used a fake address, or deleted their account. Remove these invalid email addresses from your list immediately. Many email services handle this automatically, but always verify. Consider using double opt-in to prevent this issue by confirming addresses before subscribers officially join your list.
Nonexistent domain
When you get this hard bounce error, it means the domain part of the email address (everything after the @) doesn’t exist. Maybe the company went out of business, or someone intentionally entered a fake domain. Don’t waste time fixing these—remove them from your list immediately. If that person wants to hear from you again, they’ll resubscribe with a working address.
Email authentication failure
Email authentication is your digital message security check. Email servers verify your sending domain’s identity using multiple security protocols, including:
- DomainKeys Identified Mail (DKIM)
- Sender Policy Framework (SPF)
- Domain-based Message Authentication, Reporting, and Conformance (DMARC)
If something looks suspicious, your email might get blocked, and you’ll receive a hard bounce response. Unless you fix this, your emails might never reach their destination. So, always work with your IT team to keep these security checks tight.
A damaged sender reputation can wreak havoc on your email deliverability. When you’re marked as a potential spammer, email providers will automatically reject your messages before they even have a chance to be delivered. The only way to resolve this hard bounce error is by working directly with the block list to clear your name and restore your email sending privileges.
Key takeaways
- Bounce basics: Email bounces are delivery failures that can block your messages from reaching recipients.
- Reputation risk: Too many bounced emails can mark you as an unreliable sender, damaging your email credibility.
- Technical hurdles: Different email servers have unique requirements that can unexpectedly block your messages.
- List hygiene: Regularly cleaning your email list prevents persistent delivery problems.
- Tracking matters: Monitoring soft and hard bounce error messages helps you diagnose and fix email communication issues.