If you've ever encountered the email bounce error 5.1.2, you know how frustrating it can be. This error typically occurs when you try to send an email, but it fails to reach the intended recipient due to various reasons. Understanding the causes of this error and how to resolve it is essential for ensuring smooth email communication. In this comprehensive guide, we'll delve into the details of the email bounce error 5.1.2, its common causes, and effective solutions to overcome delivery issues. By the end of this article, you'll be equipped with the knowledge to tackle this error and ensure successful email delivery.

What is Email Bounce Error 5.1.2?

Email bounce error 5.1.2 is a non-delivery report (NDR) code that indicates a temporary delivery failure. When you encounter this error, it means that the email you sent was not delivered to the recipient's mailbox. Instead, it bounced back to the sender with the error code 5.1.2. This error code specifically denotes a mailbox full or quota exceeded issue.

Common Causes of Email Bounce Error 5.1.2

1. Mailbox Quota Exceeded

One of the primary causes of the 5.1.2 email bounce error is when the recipient's mailbox has reached its storage capacity or quota. When the mailbox is full, it cannot accept new emails, resulting in the bounce-back of your message.

2. Large Attachments

Sending emails with large file attachments can also trigger the 5.1.2 error. If the size of the attachment exceeds the recipient's mailbox size limit, the email fails to deliver and bounces back with the error code 5.1.2.

3. Email Server Configuration

In some cases, the email server's configuration can contribute to the 5.1.2 error. Incorrect settings or limitations set by the recipient's email server can prevent the delivery of your email and result in a bounce-back.

4. Invalid Recipient Address

If the recipient's email address is invalid or no longer exists, your email will bounce back with the 5.1.2 error. It's essential to double-check the recipient's address for any typos or changes.

5. Temporary Server Issues

Temporary server issues on the recipient's side can also lead to the 5.1.2 email bounce error. These issues could include server downtime, maintenance, or network connectivity problems, preventing the successful delivery of your email.

Solutions to Resolve Email Bounce Error 5.1.2

1. Contact the Recipient

If you encounter the 5.1.2 error, the first step is to contact the recipient and inform them of the issue. They may need to take action to clear their mailbox, increase their storage capacity, or provide an alternative email address for communication.

2. Reduce Attachment Size

If you're sending large attachments, consider compressing or resizing them to reduce the file size. This can help ensure that the email falls within the recipient's mailbox size limits and avoids triggering the 5.1.2 error.

3. Verify Recipient Address

Double-check the recipient's email address for any errors or changes. Ensure that you have the correct and valid email address before sending your message to avoid unnecessary bounce-backs.

4. Retry Sending

In some cases, the 5.1.2 error may occur due to temporary server issues. Wait for some time and retry sending the email. If the error persists, consider reaching out to the recipient or their email service provider for further assistance.

4. Consult Your Email Service Provider

If you frequently encounter the 5.1.2 error or face difficulties resolving it, it's advisable to consult your email service provider. They can offer insights into the specific error and provide guidance on resolving delivery issues.


Dealing with the email bounce error 5.1.2 can be challenging, but with the right understanding and solutions, you can overcome delivery issues and ensure successful email communication. By addressing the causes mentioned in this article, such as mailbox quota exceeded, large attachments, server configuration, invalid recipient address, and temporary server issues, you can minimize the occurrence of the 5.1.2 error. Remember to reach out to the recipient, optimize attachment sizes, verify recipient addresses, retry sending, and seek assistance from your email service provider when needed. By following these steps, you'll enhance the deliverability of your emails and maintain effective communication with your contacts.