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How to Merge Two MBOX Files – 2 Easy Methods

Published By Nilesh
Aswin Vijayan
Approved By Aswin Vijayan
Published On January 24th, 2024
Reading Time 5 Minutes Reading

MBOX file format is a common email storage format which stores email messages in a single text file. A number of popular email clients use MBOX format to store all emails from one mailbox in a single file. The main feature of any email client is the configuration of multiple email accounts. Each email account has a number of folders and each folder is stored as one MBOX file. So think about the number of mailboxes when one has three to six accounts in a single email application! So many accounts with various folders containing tons of messages. All points towards data duplication, slow processing, and searching mechanism, etc. So what to do about it? Its simple- Merge them all into a single file. Next, how to merge multiple MBOX files into single file? Read the sections below to know about merging techniques along with the need to combine mailboxes.

Reasons to Merge Multiple MBOX Files

Let us take a look at two queries first to understand the needs behind combining mailboxes:

“Hey! I have been using Apple Mail email client for past 5 years to manage my 4 accounts. Due to professional reasons, I had to change my platform to Windows and use Outlook instead. So how can I merge all my mailboxes from all 4 accounts into a single file and access it in Outlook?”

“Hi, I use Thunderbird client to manage 6 different email accounts. It has become increasingly difficult for me to handle so many folders of each account. I am not able to search for particular emails because of duplicity. Is there a way to address this problem? Suggest me a solution, if any!”

We can easily conclude various reasons which could cause users to merge two MBOX files into one. They are as follows:

  • To refine the searching mechanism of specific emails.
  • To remove the duplication issues and free up some storage space in the process.
  • In order to access the merged file in other email clients such as MS Outlook.
  • To organize the data from multiple mailboxes in a single file.

Manual Technique to Merge two or more MBOX Files

To merge multiple MBOX files, you need an email client that supports MBOX format. Mozilla Thunderbird and Apple Mail are the two best examples of such email platforms. These two are free applications and thus are suitable to use by all users.

  • Open an email client that supports MBOX files. Examples include Mozilla Thunderbird, Apple Mail, etc. Here, we are selecting Thunderbird since it is available for both Mac and Windows.
  • Create a new folder in “Local Folders” where you want to merge the MBOX files.
  • Now, go to Tools >> Add-ons and Themes and search for “ImportExportTools NG” add-on. Install it in Thunderbird.
  • Then, right-click on the New Folder and select ImportExportTools >> import mbox file option.
  • Choose all the MBOX files from the system that you want to merge.
  • Once both MBOX files are imported, the emails from both files will appear in separate folders in your email client.
  • Open one folder and select all the email messages with Ctrl+A key. Then, right-click on one selected message and choose Move to >> Local folders >> select the second folder.
  • With this, you have moved all the emails from one MBOX file into another, technically merging them together.
  • Finally, right-click on the folder containing all the emails and go to ImportExportTools >> Export folder. This way you can export the folder as a merged MBOX file.

Combine Several Files into a Single PST

Microsoft Outlook is so popular that users of other email clients switch to Outlook one after another. There are several scenarios where a user with multiple accounts (data of each account is stored in separate MBOX files) wish to consolidate them and use in Outlook. In such cases, you have two choices:

  • Either merge the MBOX files together then convert the merged file into PST
  • Or merge and convert them together

You can use the best MBOX to PST Converter software for both. If you have already merged the MBOX files, then simply use the software to convert the file. Else, you can import the MBOX files into the software and do the following to merge and convert them together:

Steps to follow:

  1. Download, install and then, launch the tool
  2. start the mbox merge software

  3. Click Add File to select multiple MBOX files to merge
  4. click add file option

  5. Select the MBOX Files or MBOX supported email client you are currently using from the list
  6. select the mbox option or email clients

  7. Select one of these options:
    Default profile configured: For automatic fetching of data from its default location
    Select file(s)/folder from file system: For users to fetch the data from any desired location(we will be selecting this option for this procedure)
    Click Next
  8. choose the second option

  9. Tick the Use Folder Mode checkbox and browse to select multiple MBOX files
  10. select the folder containing mbox files

  11. After selecting the desired folder containing multiple mailboxes you want to merge, click Process
  12. process the added mbox files

  13. On the preview window, click the Export button to proceed.
  14. click export on the preview window

  15. Set export file format as PST. Tick the option Create single PST for all MBOX files to merge all MBOX files into one.
  16. tick the create single PST for all MBOX files option

  17. Click on Export button to combine and convert all added files into a single PST file
  18. click on export to start the process

  19. Once the process is completed, click on Open Location to access the merged mailbox.
  20. locate merged file


    Email clients often handle a lot of accounts consisting of a number of folders. Due to this, the searching and retrieval of specific emails become difficult for users. Duplicity is also a major concern in such cases. The best way to overcome these concerns is by merging all those mailboxes as one. In this article, we discussed different methods to merge two MBOX files into one. The manual method focuses on merging several MBOX files together using Mozilla Thunderbird application. While the automated tool works best when you need to both merge and convert the files together.