Migrating your email data from Microsoft Outlook (PST) to Mozilla Thunderbird is a common problem for many users who lack complete information on the process. Before understanding this process, it’s important to know that Thunderbird does not natively support the PST file format. PST files, also known as Personal Storage Tables, store Microsoft Outlook emails, contacts, calendar, and other data.
Let’s now learn how to import PST into Thunderbird using Outlook and other solutions in 2026.
Why the Need to Migrate Data to Thunderbird?
Many new users may not be familiar with Thunderbird, so I would like to mention that it is a very popular email client with many users worldwide. There are several reasons for moving data to it, such as:
- Desire for an open-source email client
- No subscription fees
- Better privacy and extensibility
- Cross-platform support
However, the problem is that Thunderbird does not directly read PST files, so you need to convert or import them using indirect methods or tools.
Method 1 — Import PST via Outlook (Windows only)
To use this method, you must have Outlook installed and configured on your Windows system.
The steps are as follows:
Install Outlook and Thunderbird
Ensure that both email clients are installed on your computer and that Outlook is configured. Otherwise, this method will not work.
Set Outlook as the default mail client
Go to Windows Default Apps settings and select Outlook as your default email application.
Open Thunderbird’s Import Tool
- In Thunderbird, go to the Tools option → Select Import
- Choose the option to import mail from Outlook.
- Follow the on-screen instructions.
Notes: This method does not directly import PST files; Thunderbird reads and saves Outlook mailboxes through the installed Outlook client and MAPI interface.
If Outlook is not properly installed/configured, you may receive a “No profile found” error.
Disadvantages of this method:
This only works for Windows systems because Outlook PST files are only used on Windows.
It depends on Outlook and Thunderbird being compatible (same bit-depth).
It does not allow you to select individual PST files unless they are associated with an Outlook profile.
Method 2 — Convert PST to MBOX and Import (Cross-Platform)
To convert your .pst file to .mbox format, you will need to use a reliable converter tool. Here we recommend MailsDaddy PST Converter as it is highly praised by many professionals. This solution offers several conversion options, including MBOX, into which you can convert your data.
To use MailsDaddy Converter for PST, you can follow these steps:
- Download and install the software on Windows machine.
- Launch the software and click on the “Auto-load/ Browse” button then browse and select the PST file that you want to convert.
- Click on Export button to perform batch PST file Conversion.
- Select MBOX file file format.
- Browse the destination then click on Export to start the conversion process.
Once the data is converted to MBOX, you can open it in Thunderbird by following the steps below.
- Install ImportExportTools NG in Thunderbird
- Open Thunderbird
- Go to the Add-ons Manager
- Search for and install ImportExportTools NG
- Import MBOX files
- Restart Thunderbird
- Right-click on Local Folders → ImportExportTools NG → Import MBOX file
- Select your converted MBOX files and import them
Advantages and Disadvantages
- Works on all operating systems
- No Outlook required
- Allows you to select specific folders
- Maintains folder structure
- Requires third-party conversion
- Some tools are paid (although free demos are available)
Final Word
In this article, I have discussed both manual and third-party tools for exporting PST files to Thunderbird accounts. Any user who wants to import their Outlook mailbox into Thunderbird can follow this guide and easily perform the conversion. The free demo version of the solution allows you to experience the working steps and functionality by exporting a few emails from each folder.
