Welcome to our comprehensive guide on email bounce back reasons. As an expert in email deliverability, I understand the frustration of having your emails bounce back and not reaching the intended recipients. In this article, we will explore the common reasons behind email bounces and provide you with valuable insights on how to prevent them. By the end, you will have a clear understanding of the factors that impact email deliverability and strategies to ensure your emails reach the inbox.

What is Email Bounce?

Email bounce occurs when an email fails to reach the recipient's inbox and is returned to the sender. Bounces can be categorized into two types:

Soft Bounce: A soft bounce is a temporary failure to deliver an email. It could be due to reasons like a full mailbox, server issues, or the recipient's email server being temporarily unavailable.

Hard Bounce: A hard bounce is a permanent failure to deliver an email. It occurs when the email is sent to an invalid or non-existent email address.

Common Email Bounce Back Reasons

Let's explore the most common reasons why emails bounce back:

1. Invalid or Non-Existent Email Address

One of the primary reasons for email bounces is sending emails to invalid or non-existent email addresses. This could be due to typos, outdated email addresses, or fake addresses entered by users.

2. Full Mailbox

If a recipient's mailbox is full and exceeds its storage capacity, incoming emails will bounce back. This often happens with email accounts that are not regularly monitored or maintained.

3. DNS Configuration Issues

Domain Name System (DNS) plays a crucial role in email delivery. Misconfigured DNS settings can lead to email bounces. It's important to ensure that your DNS records, including MX, SPF, and DKIM, are properly set up.

4. Email Content Triggering Spam Filters

If your email content or subject line triggers spam filters, your emails may bounce back or land in the recipient's spam folder. Avoid using spammy words, excessive capitalization, and misleading subject lines.

5. Sender Reputation Issues

Your sender reputation plays a significant role in email deliverability. If your sending IP or domain has a poor reputation due to previous spam complaints or blacklisting, your emails are more likely to bounce.

6. Email Size or Attachment Limit

Emails with large attachments or exceeding the recipient's email server's size limit can bounce back. Consider compressing large attachments or using file-sharing services for sending large files.

7. Recipient Email Server Issues

If the recipient's email server is experiencing technical issues or undergoing maintenance, it can result in email bounces. In such cases, the bounce is temporary, and the email may be delivered later.

Preventing Email Bounces

To minimize email bounces and improve deliverability, consider the following strategies:

1. Use Double Opt-In

Implement a double opt-in process to ensure that subscribers provide valid email addresses and confirm their intention to receive your emails. This helps eliminate typos and reduces the chances of sending emails to invalid addresses.

2. Regularly Clean and Update Your Email List

Perform regular email list maintenance to remove invalid or inactive email addresses. Use email verification tools to identify and remove hard bounce addresses from your list.

3. Verify Email Addresses Before Sending

Use email verification tools to validate email addresses before sending your campaigns. These tools check the syntax, domain validity, and mailbox existence to minimize the risk of bounces.

4. Follow Best Email Practices

Adhere to email marketing best practices, such as using an authenticated sending domain, including an unsubscribe link, personalizing your emails, and segmenting your audience. This helps improve engagement and reduces the chances of your emails being marked as spam.

5. Monitor Sender Reputation

Regularly monitor your sender reputation using tools like Sender Score or Barracuda Reputation Blocklist to identify and resolve any issues that could impact deliverability.


Understanding the reasons behind email bounces is essential for successful email marketing campaigns. By addressing the common causes of email bounce backs and implementing preventive measures, you can significantly improve your email deliverability and ensure that your messages reach the inbox. Remember to regularly monitor and maintain your email list, follow best email practices, and keep track of your sender reputation. With these strategies in place, you can minimize email bounce backs and achieve better engagement with your audience