How do I Convert OST to MBOX Files with Attachments

Summary: In the case of Microsoft Outlook, all the data are in the OST file format. Without converting the email of OST files into any other file format, it is impossible to view the files inside it. Most Outlook Users shifting to Thunderbird need to convert OST emails to MBOX to migrate all emails. Using this blog, you can avail efficient and secure ways to convert OST to MBOX. You can go for several methods, such as using the manual approach and opting for the advanced solution by using the software OST to PST Converter. Go through our write-up from top to bottom and select the methods that suit you best to import OST to Thunderbird. Now let’s further discuss in detail an OST and MBOX file format.


What is the Difference Between an OST and an MBOX File?

There are multiple differences between an OST and MBOX file format Based on the parameters such as description, email client support, and file size limit.

ParametersOST File FormatMBOX File Format
DescriptionOST files are known to be Outlook Data Files. It’s been supported by Microsoft Outlook and helps users work Offline Mode. It can store account information and data such as Email Messages, tasks, calendars, contacts, etc.MBOX is the file format used to collect messages from electronic mail. It stores a desired folder’s messages in a separate database file.
Email client SupportsTwo Email Clients, such as Microsoft Outlook and Exchange Server, support OST FIle.Multiple Email Client supports the MBOX File format, such as Mozilla Thunderbird, Apple Mail, Eudora, etc.
Size Limit of FilePreconfigured limit of 50 GBIn MBOX there is a limitation of 4.7 GB.

Why Is It Necessary to Convert OST to MBOX File?

More than 30+ email clients/ services use the MBOX file format. Emails, Contacts, Calendars, Notes, etc. These multiple items can be stored in MBOX file format. Sometimes users need to import the OST folder into Thunderbird. Apple Mail etc., which supports MBOX file format only. Due to this reason, we need to convert the OST File to MBOX file format. There can be multiple other reasons to export emails from Outlook OST to MBOX, such as:

  • To preserve the data when there is an accidental crashing of Outlook and Exchange Server.
  • When the user wants to shift from Outlook email client to Thunderbird email client.
  • When the user switches their job profile from one workplace to another.
  • OST files cannot be opened until and unless we convert OST to PST file format.
  • Mozilla Thunderbird offers many unique features compared to Outlook.

There can be multiple reasons why people need to convert OST emails to MBOX. Now let’s proceed with the methods to migrate all emails from an OST file to MBOX.

How Do I Manually Convert OST to MBOX?

Manually conversion of OST files to MBOX format is not a single-step process. Firstly, you need to change OST files into PST files. After that, you need to convert PST file into MBOX to open them.

Two-step process to convert OST file to MBOX:

  1. Convert OST to PST using Outlook
  2. Import the PST file into MBOX using Thunderbird

Step 1: Convert OST to PST by Using Outlook

There are two various ways by which you can convert your OST files into PST, so let’s move forward to learn both procedures.

Method 1: Save OST Emails to PST Using the Import/Export Option

Steps to convert OST to PST using Import/Export options are as follows-

  1. Install the Outlook application on your system or PC.
  2. Select the File menu and click on the Open & Export tab.
  3. Now, Hit on the Import/ Export option to Import the OST File .
  4. In the export to a file option, choose the export to a file option and click the Next Button.
  5. After this, Select Outlook Data File (.pst) and click the Next button.
  6. Choose the folder to export the data and click the Next button.
  7. After this, hit the Browse icon to find the specific location for the exported file.
  8. Pick the file and tap on the Open button.
  9. In the end, select the other option as per your choice and click on the Finish button.

This is one way to export OST to PST by using Import/Export option in Outlook. However, if you have any difficulty following the above process then you can also opt for the next technique to save OST into PST file format.

Method 2: Convert OST to PST Using Archiving Method

When the archiving option is enabled, Outlook emails from OST files are preserved in a separate PST file. However, keeping the old mailbox contents in the archive folder also aids in maintaining a healthy mailbox size.

The step to convert OST to PST using archiving method are as follows:

  1. Install the Outlook application on your system.
  2. Select the File tab and click on the Options tab.
  3. Now, Go for the Advanced tab and click on the Auto Archive settings .
  4. After this, choose the number of days for Auto-Archiving to Run to save the archived file.
  5. Select the folder, and provide archiving options. Press OK .

Following the steps mentioned above, the OST mailbox items from your account will be transferred to the PST files based on Archiving settings. Now, let us import the PST file to MBOX to complete the process of converting OST to Thunderbird.

Step 2: Import the PST file into MBOX Using Thunderbird.

  1. Launch the Mozilla Thunderbird on your system or PC.
  2. Click on the Thunderbird menu icon and click on the Tools option.
  3. Now, Choose the Import tab to import the Outlook PST file. After that, pick the Mail items and hit the Next Button.
  4. Pick the file type as Outlook and click the Next button.
  5. In the end, Your PST file is successfully imported. Hit the Finish tab.

As you see, the manual conversion of OST files to MBOX format is complete. But the manual approach also has some limitations because users search for alternatives to convert OST files to MBOX. Let us further discuss some limitations in detail in a manual approach.

Loopholes of Using the Manual Approach

  • To convert OST to MBOX, the whole process is lengthy and time-consuming as the user cannot convert it directly as it takes multiple steps in the complete process.
  • Users need to have technical knowledge to perform manual methods. Otherwise, it can be complicated for non-technical people.
  • By using this manual method, there can be high chances of data loss due to connection loss and internal bugs and viruses.

To avoid such problems, we suggest an alternative approach to convert the OST file to MBOX file format. This solution is 100% trustworthy, and IT professionals strongly recommend it. So continue to know more about the advanced solution to import your OST files into Thunderbird in one go.

Advanced Solutions for Conversion of OST files to MBOX format

OST to PST Converter is the top notch tool to export emails from Outlook OST to MBOX. This software is known for its effectiveness and efficiency as a benefit. Using these tools, users can convert OST files to many other files such as PST, MBOX, MSG, EML, EMLX, CSV, etc. It also migrates OST files to Office 365, Gmail, Thunderbird, Amazon WorkMail, etc. In addition, it is compatible with all versions of Windows versions. Now let’s see the step-by-step procedure to migrate data from Outlook OST to MBOX.

Step-by-Step Guide to Convert OST to MBOX Files

  1. Download, Install, and Run the OST to PST Converter software on your system.

    OST to PST Converter Step 1
  2. Choose the option Single file/ Multiple FIles and click the Next Button.

    OST to PST Converter Step 2
  3. Note :- You can also select the folder by selecting the option Select Folder icon.

  4. Click on the option Select files . Choose the OST file from your systems and hit on the Open button.

    OST to PST Converter Step 3
  5. Select the file and hit the Next button

    OST to PST Converter Step 4
  6. A Tree structure data will appear on the left side; choose the emails you want to import into MBOX ( Thunderbird ) file format. Also, you can take a preview of emails of your selected OST file. Click on the Next button.

    OST to PST Converter Step 5
  7. After this, a new window will appear under the option Saves/ Backup/ Migrate as an option to select the MBOX file format .

    OST to PST Converter Step 6
  8. On the same page, you will see multiple features such as:
    • Remove Duplicates based on To, From, Subject, Bcc, Body
    • Store in Same ( Source and path folder are same ).
    • Maintain Folder Hierarchy .
    • Migrate or Backup Emails without attachment files .
    • Date Filters : This filter converts files for specific date periods by providing start dates and End dates.
    • The custom folder Name permits you to enter the Output Folder Name.

    Note: Choose the features as per your requirements.

    OST to PST Converter Step 7

  9. Click on the option Path to Save and hit the Convert button.

    OST to PST Converter Step 8
  10. In the end, the process to convert OST emails to MBOX is completed. You can click on the Download Report button to download the data.

    OST to PST Converter Step 9


In the above write-up, we have discussed and elaborated the step-by-step guidelines of both manual and advanced procedures to convert OST to MBOX file format. However, the manual method has some limitations, while the contrary, professional method is more effective and reliable. You can opt for any of the methods at your convenience, but we suggest the professional approach as it is highly recommended by professionals to export emails from Outlook OST to MBOX.

Frequently Asked Questions

Q. How do I convert multiple OST files in one attempt?

Ans- Multiple OST Files can be converted to any other File format in just a single attempt by using the OST to PST Converter Software. It is the most reliable and efficient tool that converts single/ multiple files and can also convert the full folder.

Q. Does this tool support Windows 11?

Ans- Yes, the OST to PST Converter tool is compatible with all Windows versions, including Windows 11. This software is more effective and provides 100% higher precision.

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About The Author:

As a Technical expert, I love to write blogs on email migration, data recovery, and cloud migration. In my free time, I like to research new things related to technology.

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