As an Outlook user, encountering email bounce backs can be frustrating and hinder your communication efforts. When an email you sent bounces back, it means that the message was not delivered successfully to the recipient's mailbox. Understanding why email bounce backs occur and how to resolve them is crucial for effective email communication. In this comprehensive guide, we will explore the common causes of email bounce backs in Outlook, provide troubleshooting steps, and offer solutions to ensure your emails reach their intended recipients.

What is an Email Bounce Back?

An email bounce back, also known as a non-delivery report (NDR) or bounce message, is a notification you receive when an email you sent cannot be delivered to the recipient's mailbox. Bounce backs are generated by the recipient's email server and provide information about the reason for the delivery failure.

Common Causes of Email Bounce Backs in Outlook

1. Invalid or Non-Existent Email Address: If the recipient's email address is misspelled or doesn't exist, the email will bounce back.

2. Recipient's Mailbox is Full: If the recipient's mailbox has reached its storage limit, incoming emails will bounce back until space is freed up.

3. Temporary Server Issues: Temporary issues with the recipient's email server, such as maintenance or congestion, can result in bounce backs.

4. Blocked Sender: If the recipient's email server has blocked your email address or domain, your emails will bounce back.

5. Attachment Size Limit: If your email contains attachments that exceed the recipient's email server's size limit, the email will bounce back.

Troubleshooting Steps to Resolve Email Bounce Backs

When you encounter an email bounce back in Outlook, follow these troubleshooting steps:

Check the Recipient's Email Address: Verify that the recipient's email address is correct and properly formatted.

Resend the Email: If the bounce back was a temporary issue, try resending the email.

Reduce Attachment Size: If the email contains large attachments, consider compressing or removing them to avoid size limit issues.

Contact the Recipient: If the issue persists, contact the recipient through an alternative communication channel to ensure their email address is valid and functioning.

Solutions for Email Bounce Backs in Outlook

To address common causes of email bounce backs in Outlook, try these solutions:

Verify Recipient's Email Address: Double-check the recipient's email address for accuracy and typos.

Clear Recipient's Mailbox: Advise the recipient to free up space in their mailbox by deleting unnecessary emails.

Resend Email at a Later Time: If the bounce back was due to temporary server issues, try resending the email after some time.

Ensure Sender Authentication: Configure your email server with proper authentication, such as SPF, DKIM, and DMARC, to prevent your emails from being blocked or marked as spam.

Use File Sharing Services: Instead of sending large attachments via email, upload the files to a file sharing service and share the download link with the recipient.

Commonly Asked Questions about Email Bounce Backs in Outlook

Q: How can I prevent email bounce backs?

A: To minimize email bounce backs, ensure that you have accurate and up-to-date recipient email addresses, regularly monitor your email deliverability, follow best practices for email sending, and maintain a good sender reputation.

Q: Can email bounce backs be caused by the recipient's email settings?

A: Yes, email bounce backs can be caused by various factors on the recipient's side, such as full mailbox, email filtering settings, or blocked senders.

Q: Are there any tools to help prevent email bounce backs?

A: Yes, there are email verification and validation services available that can help you verify the validity of email addresses before sending. These tools can reduce the chances of encountering bounce backs.

Q: How can I improve email deliverability in Outlook?

A: To improve email deliverability in Outlook, focus on maintaining a clean and engaged email list, following email marketing best practices, using proper authentication methods, and monitoring your sender reputation.


Email bounce backs in Outlook can disrupt your communication efforts, but by understanding the common causes and implementing the appropriate solutions, you can minimize delivery failures and ensure your emails reach their intended recipients. Follow the troubleshooting steps outlined in this guide and consider the solutions provided to overcome email bounce backs effectively. By doing so, you can enhance your email deliverability, maintain strong sender reputation, and optimize your email communication in Outlook.