Convert PST and OST files to MBOX

Outlook for Microsoft 365, Outlook 2021, Outlook 2019, Outlook 2016, Outlook 2013, Outlook 2010, Outlook 2007
Thunderbird version 38 and newer versions

The normal Thunderbird import process requires that you have a compatible version of Outlook installed on your computer. To import emails from Outlook to Thunderbird, Outlook must be set as your Default email client. If you don't have Outlook installed, there are alternatives listed below. If you are looking for a solution to convert pst to mbox, ost to mbox and migrate from Outlook to Thunderbird, follow these steps to import pst to Thunderbird.

Thunderbird Import PST Files Wizard

Thunderbird Import Wizard for Outlook was disabled in Thunderbird version 38 because it broke. This was fixed in Thunderbird version 58. If it crashes again, you can work around this by temporarily using an older version of Thunderbird, import your data, and then update Thunderbird to the latest version.

  1. In Thunderbird, go to Tools > Import….
  2. Choose Mail and click Next.
  3. Choose Outlook as the file type and click Next.
  4. Wait for the import to finish and click Finish.

Outlook is not installed

An alternative to Thunderbird's Import Wizard is to use a tool to transform your data to mbox format (.mbx), and then copy mbox files into Thunderbird Local Folders. There are a few such tools for Outlook to mbox conversion: PST to MBOX Converter, OST to MBOX Converter, OST PST Viewer.

PST to MBOX Converter and OST to MBOX Converter are one-click converters to convert entire Outlook data file to .mbox file format. If you need to convert selected emails from Outlook to mbox, or if you have data issues or crashes with Thunderbird Import Wizard for Outlook use OST PST Viewer.

Import Outlook data files to Thunderbird

There are steps to import .pst and .ost files into Thunderbird with OST PST Viewer.

1. Find your local .pst and .ost files

Outlook saves .pst and .ost files in a variety of different locations. Depending on what type of account you have, see the locations for Outlook 2007, Outlook 2010, and Outlook 2013, 2016 for example.

2. Open your .pst and .ost files

Download OST PST Viewer and browse for the .pst and .ost files. You will probably have several Outlook data files that need to be imported into Thunderbird.

3. Convert your emails to mbox or eml format

Select mailbox root folder in All folders pane, and click File > Export. Choose MBOX file format and click Ok.

Convert .pst to mbox files

Wait for the export to finish.

4. Find your Thunderbird "Local Folders" Directory

Launch Thunderbird. Right click on "Local Folders" and select "Settings". Now you can see "Local directory" for your "Account Settings".

Outlook Import

Something like this:
C:\Users\%username%\AppData\Roaming\Thunderbird\Profiles\7l36jvtj.default\Mail\Local Folders
(You need to have allowed "Show hidden files, folders, and drives)

5. Copy mbox files into Local Folders

Quit Thunderbird. Navigate to your Thunderbird "Local Folders" directory in an explorer and drag and drop your mbox files in there. The result mbox files are:

  • The .sbd folders - used to store the folder hierarchy.
  • The files that actually contain your messages (do not have any three-letter extension at all): Archive, Calendar, Contacts, Inbox,..

6. Browse mbox

Restart Thunderbird, and you should see the exported Outlook mailbox in your Thunderbird Local Folders list.

Can I import contacts, calendar and tasks into Thunderbird?

Thunderbird contacts, calendar and tasks are not a part of the mbox file. Outlook contacts, calendar and tasks can be exported to mbox as emails.

Updated on July 16, 2023

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See Also

PST to MBOX Converter

Convert Outlook PST and OST files to Thunderbird MBOX files. Maintains the original folder structure after the conversion.

OST to MBOX Converter

Convert Outlook PST and OST files to Thunderbird MBOX files. Convert emails, attachments, contacts, notes and tasks.

Convert MBOX to PST

This tool converts MBOX (Thunderbird, Apple Mail, etc.) files to Outlook. Maintains the on-disk folder structure of the mbox mailbox after conversion. Import mbox into existing or a new Outlook Data File (.pst and .ost).