How to Open Large MBOX File in Windows and Mac? Top 5 Ways

  

Mark Regan
Published: August 21st, 2025 • 10 Min Read

Do you have multiple data files with the .mbox extension and want to open MBOX files to access all your data seamlessly? If it sounds appropriate, then you are on the right blog. Here, we will explain the best methods to open large MBOX files Windows and Mac machines with or without email services. Plus, we will also share a free professional solution that every expert uses and recommends to read MBOX files in bulk.

Thus, MBOX files are a standard file format that stores all the data, including email messages and attachments, in a single database. This file extension is supported by many well-known email clients such as Thunderbird, Apple Mail, Eudora, etc. However, only a few applications allow the user to open MBOX file without any issue.  Moreover, there are four types of MBOX files supported by different platforms. For example, MBOXO is supported by Eudora.

Hence, to learn more about how to open MBOX file in Windows and Mac operating systems without any hassle, read the complete guide and follow the method that works best for your case. Make sure to choose the solution that is reliable and easy to follow.

Important Note: Download the professional utility to open large MBOX files without installing any extra applications or navigating to the default location of MBOX files. Thus, the advanced solution automatically fetches the configured account and its MBOX files.

Preparations to Open MBOX File Data

Some of the basic steps that one should keep in mind or follow before practicing any method to read MBOX files Windows and Mac are as follows:

• Thunderbird, Apple Mail, Postbox, or other MBOX-supportable email clients must be installed on the device.
• Take a backup of MBOX file to create a copy of your data for just in case you lose it while following the manual way to open large MBOX files.
• Make sure you are opening a healthy MBOX file, because these methods will not work with corrupt data files.
• Before following the right way of how to open MBOX file in Windows, make sure to save all your files in one folder to manage them for quick processing.

How to Open MBOX File in Windows & Mac Machines?

We will access data using Thunderbird, Apple Mail, Chrome, and a free solution for both Mac & Windows machines. All the methods are given below one by one, use them according to your requirements to open large MBOX files.

#1: Read MBOX File Windows

This is one of the most prominent solutions of how to open MBOX file in Windows. However, before following this, make sure to install the “ImportExportToolNG” add-ons on your Thunderbird profile to activate the import MBOX to Thunderbird feature and thus, open MBOX file successfully. Once done, follow the below mentioned steps:

1. Open the Thunderbird desktop application on your computer.
2. Log in to your account and go to the “Tools” tab from the ribbon.
3. Choose the “ImportExportTools” and then select “Import MBOX Files” option from the list.

   

4. After that, select the “Import Directly One or More Files” and then the “OK” icon.

   

5. Choose the MBOX file you want to open on your computer.

   

6. Click on the “Open” button at the end to read MBOX file Windows data.
7. And with this, all your MBOX files will be available in Thunderbird to read them.

   

#2: Open MBOX File Online

All browsers, including Chrome, support the .html format to open any file data, so first we have to convert MBOX files to HTML. Thus, you can do it either by following the linked page or by following the steps mentioned below:

1. First of all, upload your data files to your Thunderbird account.
2. Once done, right-click on the imported MBOX file.
3. Again, select the “ImportExportTools ” option.
4. Now, choose the “Export All Messages in a Folder” button.
5. After that, hit the “HTML Format” option.
   
6. And select any path to save the exported file.
7. Finally, hit the “Select Folder” icon.
8. After this, go to the saving location of the output and double-click on it to open MBOX file online.

#3: Read MBOX File in Mac

One of the best solutions of how to open MBOX file mac is via Apple Mail, and hence, the steps for it are mentioned below:

1. Firstly, log in to your Apple Mac Mail.
   
2. Then, find and select the “File” tab.
3. Next, select the “Import Mailboxes…” from the list.
   
4. After that, choose “Files in MBOX Format” and then hit the “Continue” button.
   
5. Further, locate the path of your .mbox file on the machine.
   
6. Hit the “Continue” button, and once files are uploaded, click on the “Done” button.
   
7. This will import MBOX file to Apple Mail and allow the user to open MBOX file mac seamlessly.

#4 Read MBOX Files/Folders in PostBox

Last but not least way to open MBOX file is via the PostBox. The quick steps of this manual solution are as follows:

1. First of all, start PostBox on your device.
2. Then, navigate to “File Menu” and click “Import”.
3. Now, browse and select the MBOX folder from its saving path.
4. Next, hit the “Import” button and wait a while to complete the import process.
5. Finally, when the process to import MBOX to PostBox completes, click and open MBOX files.

1. Firstly, download and install the tool on your PC.
   
2. Click on the “Add File” or “Add Folder” button to open MBOX files.
   
3. And then, it open MBOX files on the screen panel in the same hierarchy as it was saved.  
4. Finally, you can click on the desired email from the panel to open MBOX file with attachment.
   

Benefits of Using the Pro Tool

• It is not only a free solution but also offers an advanced version which allows the user to even convert MBOX to PST, Gmail, Thunderbird, MSG, EML, and other 30+ saving options.
• This tool is very easy to use, supports bulk actions, and has dedicated tabs, buttons, and panels for each action so that even a beginner can easily read MBOX file Windows & Mac.
• It automatically fetches the location of the MBOX data and allows the user to choose the files and folders accordingly to generate a specific and unaltered output.
• The tool also has a search option, which allows the user to find the desired MBOX file and read it with the attachment.
• By upgrading to the licensed edition, the user can seamlessly import, convert, fix, backup, and extract attachments from MBOX files in bulk by using one tool only.

Conclusion

In short, there are multiple solutions of how to open MBOX files in Windows and Mac using manual and professional ways. However, the conventional way is indirect, has lots of limitations, and is not worth relying upon. Therefore, experts always suggest downloading and using an advanced tool to access MBOX files. The pro utility maintains folder hierarchy, offers a pro version as well, works swiftly, supports batch mode and attachments, gives quality output, and even shows minorly unhealthy MBOX files.