How to Convert PST to MBOX Files for Thunderbird and Apple Mail

Why Convert PST Files to MBOX Format?

Users convert PST files for four reasons.

• Outlook Switch. Thunderbird and Apple Mail import MBOX files only. You need MBOX when you switch from Outlook.
• Orphan PST Access. You open a PST file from a backup, colleague or old server in your MBOX client after conversion.
• Cross Platform Use. MBOX files open on Windows, Mac and Linux while PST files open in Outlook only.
• License Cost. Desktop Outlook needs a paid license while Thunderbird and Apple Mail cost nothing extra.

What is the Difference Between PST and MBOX Files?

PST is the Microsoft Outlook format and stores emails, contacts, calendars and tasks in one file. MBOX stores emails only and saves a mailbox folder as one plain text file.

Our MBOX file format guide explains the format in detail. Import MBOX to Outlook converts MBOX data back to PST.

What to Check Before You Convert PST Files?

Check four points before you start.

• Copy your PST file to a safe folder and work on the copy.
• Note the PST size. Large files take longer because Outlook copies every email.
• Confirm that Outlook is installed before you try a manual option.
• List the contacts and calendars you need. MBOX stores emails only. Contacts need VCF files and calendars need ICS files.

How to Export PST Files as MBOX Manually?

You have three manual options. Two need Outlook on Windows. One needs legacy Outlook for Mac.

Thunderbird and Outlook (Free, Needs Outlook on Windows)

Thunderbird imports the PST data through Outlook. ImportExportTools NG then saves the imported folders as MBOX files. Thunderbird and Outlook must share one Windows PC.

1. Search for Default App Settings on the taskbar and set Outlook as the default email app.
2. Open Outlook and confirm that your PST data appears in the folder pane. Choose File > Open & Export > Import/Export to add the file when it is missing. Close Outlook.
3. Open Thunderbird and choose Tools > Import. Press Alt when the menu bar is hidden.
4. Select Mail in the Import window and click Next.
5. Select Outlook and click Next.
6. Close the Import window when the import ends. Thunderbird adds an Outlook Import folder under Local Folders.
7. Open Add-ons and Themes from the Tools menu and install ImportExportTools NG. Restart Thunderbird.
8. Right click the Outlook Import folder and open the ImportExportTools NG menu. Choose Folder Export (mbox) > Structured With Subfolders. Select a destination and click Select Folder.

Thunderbird saves the MBOX files in your destination folder with the same folder structure. Our guide to export Outlook email to a Thunderbird profile explains the import side.

IMAP Account (Free, Uploads Emails to a Server)

Outlook uploads your PST emails to an IMAP mail server. Thunderbird downloads them from the server and exports them as MBOX.

1. Add an IMAP account from your mail provider to Outlook.
2. Choose File > Open & Export > Import/Export and import the PST file.
3. Drag the PST folders into matching folders of the IMAP account. Outlook uploads the emails to the server.
4. Add the same IMAP account to Thunderbird and wait until the folders download.
5. Right click a downloaded folder and choose ImportExportTools NG > Folder Export (mbox) > As mbox File.
6. Open the MBOX file in a mail client or text editor to verify the emails.

   Thunderbird Save As creates EML files, not MBOX files. Use ImportExportTools NG for MBOX files. Use an account you control because this method sends your emails to a mail server.

Outlook for Mac (Free, Older Versions Only)

Legacy Outlook for Mac imports PST files, as Microsoft's import guide for legacy Outlook for Mac confirms. Outlook 2011 creates an MBOX file when you drag a folder to your desktop.

1. Open Outlook for Mac and go to Tools > Import.
2. Select the Outlook for Windows archive (.pst) option and click Continue.
3. Select your PST file and click Import. Folders appear under On My Computer.
4. Drag one folder to your desktop and repeat for every folder.

   Only Outlook 2011 on older macOS has documented support for drag to MBOX. Test one small folder in your version first. Our Outlook for Mac to MBOX guide explains OLM files.

How to Convert PST to MBOX With EmailDoctor Software?

EmailDoctor Software converts PST files to MBOX on Windows and Mac without Outlook. EmailDoctor Software also works offline with ANSI and Unicode PST files from Outlook 2000 to 2021.

EmailDoctor Software has six main features.

• Folder Hierarchy. Keep the folder structure inside the converted MBOX files.
• Date Filter. Limit the output to emails between chosen dates.
• Advance Scan. Scan a highly corrupt PST file before you convert it.
• Deleted Items. Recover permanently deleted emails into the output.
• 14+ Formats. Export MBOX, EML, MSG, PDF, PST, CSV, HTML, MHT and more.
• Email Preview. Check emails in Normal Mail View before you export.

Convert PST Files on Windows

1. Launch EmailDoctor Software on your PC.
2. Click Add File.
3. Choose Select File to browse for files or Search File to scan a drive.
4. Select the PST file in the Windows dialog and click Open.
5. Tick Advance Scan for a highly corrupt file or Recover Permanently Deleted Items for removed emails. Click Add.
6. Wait for the scan to end. Check the scanned emails in Normal Mail View.
7. Select the MBOX radio button.
8. Set a Date Filter to convert emails from a set period.
9. Click Browse and set the destination folder.
10. Select Maintain Folder Hierarchy, Don't Export Empty Folder and Ignore System Folders as needed.
11. Click Export.
12. Click OK on the success message to view the export report.

Open the destination folder to find the new MBOX files.

How to Export PST Emails as MBOX on Mac?

Apple Mail and Thunderbird import MBOX files on Mac. Mac edition of the converter opens your PST files on macOS and exports them as MBOX.

1. Open EmailDoctor Software on your Mac.
2. Use Add File(s) for single files or Add Folder for a folder of PST files.
3. Select the PST file and click Open.
4. Check the list of added files.
5. Select MBOX. Maintain Folder Hierarchy preserves the folder structure.
6. Click Advance Settings to set Categories and Date Filter. Click Save.
7. Click Change to set the destination.
8. Choose the folder where the MBOX files should go.
9. Click Export.
10. Click View Report after the success message to open the export report.

EmailDoctor Software creates one MBOX file for every PST folder.

Which Method Fits Your PST File?

Both free options depend on Outlook while EmailDoctor Software works without Outlook.

I suggest Thunderbird for one small file and EmailDoctor Software for large files, damaged files and Mac data.

What Problems Appear While Converting PST Files?

Five problems stop PST conversions.

• Import Freezes. Close Outlook before the import and confirm that Outlook is the default mail app. Retry in Thunderbird.
• Contacts Missing. MBOX stores emails only. Export contacts as VCF and calendars as ICS with EmailDoctor Software.
• PST Too Large. Split the file into smaller parts with Split PST Files before you convert it.
• Damaged PST File. Thunderbird and IMAP cannot open a damaged file. Use Advance Scan in EmailDoctor Software.
• Demo Stops at 25 Items. Demo mode converts 25 items. Activate the full version to convert every item.

Frequently Asked Questions

Final Words

People struggle with PST to MBOX conversion because Thunderbird cannot open PST files. Manual options need Outlook, Thunderbird and an extension on one PC.

Back up the PST file before you start and convert one small file as a test. Open the MBOX output in Thunderbird or Apple Mail and confirm that folders and attachments look right.

EmailDoctor Software then converts the rest on Windows or Mac without Outlook. Advance Scan opens damaged files, Date Filter limits the period and Maintain Folder Hierarchy preserves your folder order.

Want EML files instead? Convert EML to MBOX gives the steps for that format.