Convert Outlook and Exchange data files to Thunderbird (MBOX)

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 32-bit or 64-bit version of Outlook installed on your PC. To import messages from Outlook to Thunderbird, Outlook must be set as the Default mail client. An alternative to Thunderbird's import wizard is PST Walker tool to convert pst to mbox and ost to mbox or eml format, and then use Import Export Tools add-on in Thunderbird to import the files.

Thunderbird import wizard

To use Thunderbird's import pst wizard, you must use an older version of Thunderbird, because the wizard is disabled for Outlook in Thunderbird version 38 and newer versions. Install version 31.8, import your data, then upgrade to the latest version of Thunderbird via the built-in update mechanism. If you do not have it installed, there are alternatives as noted below.

Convert Outlook to Thunderbird

Whether you’re looking for a solution to migrate your emails from pst to mbox or switching to Thunderbird, there are the steps to import pst to Thunderbird.

1. Find your local .pst and .ost files

Outlook stores your .pst and .ost files somewhere in the application data folder for your Windows user: see the Microsoft Office site for the locations for Outlook 2007, Outlook 2010, and Outlook 2013 for example. You will probably have at least two mail files, both of which will need to be imported into Thunderbird. Whether they are in PST (outlook.pst, archive.pst) or OST (outlook.ost) format depends on what type of mail server and which version of Outlook you are using.

2. Convert your emails to mbox or eml format

Download and install or run portable version of PST Viewer (pstwalker.exe).

Open it, select File->Open menu to browse .pst or .ost file to open.
Select root folder in All folders pane, click the File->Export menu to convert.pst/.ost file to mbox.

Convert .pst to mbox files

3. 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)

4. Copy mbox files into Local Folders

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

5. Browse mbox

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

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