How to Convert OST to MBOX Files with Attachments?

Written By
Abhishek Singh

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Updated on
November 18, 2025

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5 minutes Read

Summary: Email migration often feels complicated, especially when dealing with formats like OST and MBOX. Convert OST to MBOX offers you full access to your Outlook data in clients such as Thunderbird or Apple Mail. This blog explains the most reliable ways to perform the conversion and introduces a dedicated MacSonik OST Converter Tool that delivers a faster, safer, and more stable experience. It’s a clear guide for anyone who wants a smooth move to a new email platform.

Why Do Users Need to Convert OST File to MBOX?

• The best way to be able to use a file converted from Outlook without Outlook is to convert it to MBOX.
• OST files are tied to an Outlook profile. Once converted to MBOX, you can have access to the data without Outlook.
• If you have deleted the Outlook profile tied to the OST file or Exchange account, converting the orphaned OST (without a profile) to MBOX can help fetch the data.
• MBOX works on Windows, macOS, and Linux. This gives you some flexibility with respect to the systems you use.
• MBOX is a good choice for long-term backup, given that MBOX is portable, human-readable, and easy to archive safely.

Manual Method to Convert OST to MBOX

There is no direct manual method to convert an OST file to MBOX, so the process is done in two stages: first exporting the OST data to a PST file, and then importing that PST into Thunderbird. Here’s how you can export OST file to MBOX:

Step 1: Export OST Data to PST in Outlook

1. Firstly, open Microsoft Outlook and go to the File menu.
2. Then, click Options, then choose Advanced.
3. Under the Export section, click Export.
4. Select Export to a File -> Outlook Data File (.pst).
5. Pick the mailbox or folders you want to export, then choose where to save the PST file.
6. At last, click Finish to create the PST file you need to convert OST to MBOX.

Step 2: Import the PST File into Thunderbird

1. Open Thunderbird, then go to Tools > Add-ons > Extensions.
2. Then, search for ImportExportTools NG and install the extension.
3. Ensure the PST file is accessible on your system.
4. After the add-on is installed, go to Tools > ImportExportTools NG.
5. Choose Import Outlook PST and select the PST file you exported.
6. Thereafter, follow the prompts to complete the import.
7. Once imported, the emails appear in Thunderbird.
8. To save them as MBOX, right-click the imported folder and choose Export, then save the folder in MBOX format.

Limitations:

• You must convert OST to PST first, which adds extra steps and time.
• The process won’t work if Outlook isn’t available or the OST is orphaned and cannot be opened.
• Importing PST files depends on third-party extensions like ImportExportTools NG.
• Large mailboxes may lose attachments, folder structure, or metadata during import.
• Exporting and importing large data sets can take a long time.
• Corrupted or inaccessible OST files cannot be exported manually.
• Handling multiple OST files manually is slow and repetitive.

Simplest Way to Convert OST to MBOX

A specialized OST to MBOX Converter Tool maintains the original structure, metadata, and attachments during conversion. It processes your files locally on the system, ensuring that no data is uploaded, stored, or shared anywhere, which protects your privacy. Along with strong data integrity, the tool provides useful features such as bulk file conversion, detailed email previews, and advanced filters to export only the data you need. Overall, it offers a safer, cleaner, and more dependable way to move your mailbox to MBOX-supported platforms without compromising security.

Steps to Convert OST Emails to MBOX

1. Download the OST Converter Tool.
2. Select the MBOX file or folder and click Next.
3. Preview and choose a file, and click Next.
4. Choose MBOX as the output format and apply the necessary filters.
5. Finally, set the path to save and click Convert.

Read this if you want to import OST files into Gmail.

Conclusion

To conclude, convert OST to MBOX is crucial for the transition from Outlook to other local email clients like Thunderbird or Apple Mail. Through a manual method, it can be tedious and confusing for someone who is not tech-savvy, and may take longer. Using a very professional OST to MBOX Converter Tool will facilitate the conversion quickly, easily, accurately, and hassle-free.

Frequently Asked Questions

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