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How to Fix the “No Valid MBOX Files Were Found” Error?

Ritu Roy | how to mac os MBOX software technology | 5 minutes read | Modified on: 09-07-2025
Fix MBOX file error macOS

A common issue faced by many macOS users is the “No valid MBOX files were found” error when trying to move MBOX files from one macOS version to another. In this article, we’ll walk you through several practical solutions to help you overcome this problem and successfully import your MBOX files without any hassle.

Different operating systems (OS) support a variety of email clients and file formats. Among these, the MBOX file format is one of the most widely used by popular email clients such as Apple Mail, Pocomail, Entourage, Mulberry, SeaMonkey, Opera Mail, Spicebird, Netscape Mail, and more. Despite its popularity, MBOX files can sometimes become corrupted, leading to error messages that interrupt your workflow.

A common issue users encounter is the “Error no valid MBOX files were found,” which typically arises when working with corrupted or incompatible MBOX files. This problem is especially common among Mac Mail users and often results from compatibility issues between different macOS versions. Differences between older and newer macOS releases can cause MBOX files to become inaccessible, triggering the “No valid MBOX files were found” error.

In this blog, we’ll explore the root causes of this error and share practical solutions to help you resolve the issue and regain access to your MBOX files.

The Root Cause of the Error ‘No Valid MBOX Files Were Found’

The “No valid MBOX files were found” error is most commonly encountered by Apple Mail users when attempting to import MBOX files. To better understand why this error occurs, here are the main causes:

  • Accessing an Incorrect Directory: The error can appear if the user tries to import MBOX files from a directory that Apple Mail does not recognize as valid.
  • Transferring MBOX Files Between macOS Versions: Moving MBOX files from one version of macOS to another can lead to compatibility issues, causing the files to become inaccessible.
  • Importing Corrupted MBOX Files: Attempting to import an MBOX file that is already corrupted will trigger this error message.

How to Fix the Issue of ‘No Valid MBOX Files Were Found’?

This issue is commonly experienced by Mac Mail users when attempting to import MBOX files from one macOS version to another, for example, migrating from macOS 10.6 to macOS 10.7. Compatibility differences between these versions often lead to the frustrating error message: “No valid MBOX files were found.”

To resolve this and successfully import your MBOX files, follow the troubleshooting steps outlined below. Before you begin, make sure to back up your Mac Mail mailbox to prevent any data loss.

Here are the commands and steps to follow:

~/library/mail/

And

~/library/preferences/com.apple.mail.plist.

How to Access the Hidden Library Folder in macOS

If you need to open the hidden Library folder on your Mac, follow these steps:

  1. Click Go in the Finder menu, then select Go to Folder…
  2. In the box labeled Go to the folder:, type ~/Library/ and click Go.

Note: To import MBOX files successfully, it’s crucial to access your previous or old messages located in the ~/Library/Mail/ folder.

Fixing the ‘No Valid MBOX Files Were Found’ Error: Step-by-Step Guide

  1. Close the Mail app.
  2. Copy messagerules.plist from the old Mail folder.
  3. Paste messagerules.plist into the new location:
    ~/Library/Mail/V2/MailData/
  4. Delete the file named messagerules.plist.backup in the current folder.
  5. Reopen the Mail app.
  6. Verify your mail rules by going to Mail > Preferences > Rules.

Steps to Import MBOX Files in Apple Mail

  1. Go to File and select Import Mailboxes.
  2. Choose Import Mailboxes again.
  3. From the list of supported MBOX-based email clients, select Apple Mail and click Continue.
  4. Locate your MBOX file, select it, and click Choose.
  5. Preview the extracted MBOX files, verify the contents, and click Continue.
  6. Restart the Mail app.
  7. Verify the imported mailbox and move emails to their original location if necessary.
  8. Check if the system’s search tool (Spotlight) is working properly.
  9. If Spotlight is not functioning correctly, rebuild its index by opening Terminal and running the command: sudo mdutil -E /

Limitations of Manually Fixing the ‘No Valid MBOX Files Were Found’ Error

While the manual method described above can resolve the “No valid MBOX files were found” error in Apple Mail, it comes with several drawbacks:

  • Lengthy and Complex Process: The steps involved are time-consuming and require careful attention to detail.
  • Technical Expertise Required: Users need a certain level of technical knowledge to execute commands correctly.
  • Risk of Data Loss: Entering incorrect commands or performing steps improperly can lead to the loss of critical data.

If you are frequently facing this error and considering switching from Apple Mail to Microsoft Outlook, a better solution might be to convert your MBOX files to PST format using a specialized tool.

Professional MBOX File Conversion Made Easy with MacArmy MBOX for Mac Tool

MacArmy MBOX Converter is a professional tool designed to convert MBOX files into PST files, which are compatible with Microsoft Outlook. Additionally, it supports exporting to other popular formats like MSG, PST, PDF, OLM, EML, HTML, CSV, Thunderbird, and more.

win download buynow

The tool is not limited to Apple Mail alone it also supports MBOX files from a wide range of email clients including Thunderbird, Google Takeout, Entourage, Spicebird, Pocomail, Eudora, Mulberry, SeaMonkey, Netscape, Opera Mail, Mozilla Mail, Evolution, and more.

Conclusion

MBOX files are widely used by several email clients such as Apple Mail, Thunderbird, and Netscape. However, Apple Mail users often face the “No valid MBOX files were found” error when importing MBOX files. Although this issue can be resolved manually, the process is complicated, time-consuming, and requires technical skills.

If manual solutions don’t work or the problem persists, switching to a different email client like Microsoft Outlook may be a viable option. This will require converting MBOX files to PST format, which can be efficiently accomplished with automated tools like MacArmy MBOX for Mac Tool. This software not only converts MBOX files to PST but also offers options to save in other formats such as MSG and EML, allowing you to back up your data or import it into various email clients with ease.