12 Top Reasons Emails Bounce (and How to Fix Them)

What is an Email Bounce?

Email marketing remains a highly effective way to engage customers and drive business results. However, one critical issue that often disrupts email campaigns is email bounces. When an email bounces, it fails to reach its intended recipient, affecting your ability to connect with your audience.

Bounced emails harm your sender reputation, reduce your deliverability rates, and derail your marketing goals. Understanding the causes behind email bounces—both hard and soft bounces—and learning how to prevent them can significantly enhance your email campaign success.

Types of Email Bounces

• Hard bounces: Permanent failures, such as invalid or non-existent email addresses.
• Soft bounces: Temporary issues like a full inbox or server problems, where delivery might succeed later.

Each bounce type can affect your campaign differently, so it’s essential to identify and address these issues promptly.

Common Reasons Emails Bounce and How to Fix Them

1. Invalid or Non-Existent Email Addresses (Hard Bounce)

An invalid or mistyped email address is one of the most common causes of hard bounces. Whether due to typos or fake addresses, sending emails to invalid addresses harms your sender reputation.

Solution:

• Implement double opt-in processes to validate new email addresses.
• Use tools like ValidifyMail to verify and clean your email lists regularly, removing inactive or invalid addresses before sending campaigns.

2. Message Size Exceeds Server Limits (Soft Bounce)

Some email servers limit the size of incoming messages (e.g., Gmail caps at 25MB). Large attachments or images can trigger soft bounces.

Solution:

• Compress images and host large files externally, providing download links instead of attaching them directly. A great tool to use is Resizer.Pro.

3. Full Inbox (Soft Bounce)

When a recipient’s inbox is full, your email can't be delivered, resulting in a soft bounce. While this is usually a temporary issue, repeated bounces may indicate an abandoned account.

Solution:

• Regularly clean your list to remove addresses that consistently bounce due to a full mailbox. Email verification tools can help you track these accounts.

4. Authentication Failures (Hard Bounce)

Emails that fail to pass authentication protocols like SPF, DKIM, or DMARC may bounce because the recipient’s server flags them as suspicious.

Solution:

• Ensure your domain’s SPF, DKIM, and DMARC records are correctly configured to enhance security and prevent authentication-related bounces.

5. Temporary Server Issues (Soft Bounce)

Sometimes, recipient servers experience temporary downtime, leading to a soft bounce. These are usually short-lived, but monitoring patterns can reveal persistent issues.

Solution:

• Set up automatic retry mechanisms for soft bounces. If the problem continues over multiple campaigns, consider segmenting these addresses for review.

6. Spam Filters and Content Rules (Hard/Soft Bounce)

Anti-spam filters analyze email content and may reject emails that seem suspicious or include flagged elements like excessive promotional language, links to blacklisted sites, or poorly formatted HTML.

Solution:

• Avoid spammy language and ensure your HTML is well-structured. Test your emails against popular spam filters before sending to reduce the risk of triggering content filters.

7. Antivirus Blocking (Hard/Soft Bounce)

Many mail servers use antivirus software to scan incoming emails. If your email contains flagged content or attachments, it may bounce.

Solution:

• Ensure your email content is safe by using trusted links and avoiding attachments that might be considered dangerous.

8. Blacklisted Domain or IP Address (Hard Bounce)

If your sending domain or IP address is flagged as a source of spam, recipient servers may automatically block your emails.

Solution:

• Maintain a good sender reputation by using clean, verified lists and following email marketing best practices. Get your email list cleaned now here.

9. Expired Domain Name (Hard Bounce)

An email domain that has expired can no longer receive messages, resulting in hard bounces.

Solution:

• Regularly validate email addresses and remove those linked to expired domains. We do suggest using ValidifyMail API to verify email ids at the source.

10. Recipient’s Email Policy (Hard/Soft Bounce)

Some servers enforce strict email policies, blocking messages based on geographic restrictions or content rules.

Solution:

• Ensure your emails comply with the recipient’s policies. For consistent bounces from a specific region or server, contact the domain’s administrator for clarification.

11. Incorrect DNS Settings (Hard Bounce)

Issues with a recipient’s DNS settings, such as missing MX records, can prevent email delivery.

Solution:

• Monitor bounce-back data for DNS-related error codes and retry sending when appropriate.

12. Email Forwarding Issues (Soft Bounce)

Email forwarding complications can cause a soft bounce if the forwarding server encounters issues.

Solution:

• Encourage recipients to update their email addresses to avoid problems with forwarding.

Why Do Bounces Matter?

High bounce rates can severely damage your email campaigns. Here’s why they matter:

• Damage to Sender Reputation: High bounce rates signal to ISPs that your email practices are poor, potentially leading to your domain being flagged as spam.
• Lower Deliverability: Continuously bouncing emails harm your deliverability, reducing the chances of reaching recipients’ inboxes.
• Risk of Blacklisting: A consistently high bounce rate can result in your IP address or domain being blacklisted.

The Need for Email List Cleaning

A clean email list is crucial for maintaining a successful email marketing strategy. Over time, email lists naturally degrade as addresses become inactive or abandoned. Regular list maintenance with ValidifyMail ensures you’re only sending to valid addresses, improving your deliverability and reducing bounce rates.

Using ValidifyMail's email verification tools can significantly improve your campaign’s success by ensuring your emails reach their intended inboxes. Don’t let bounces sabotage your efforts—verify your list today and watch your email performance soar!