How to Import PST to Thunderbird - A Complete Guide

Dec 10, 2023 | By Deepak Singh Bisht

In today's digital world, dealing with various email platforms can sometimes be challenging. One common problem that many of us face is moving our data from one email client to another, specifically, from Microsoft Outlook to Mozilla Thunderbird.

In this post, we're going to make this task as simple as possible for you, whether you're a computer expert or someone just starting to explore the digital realm. We'll provide you with easy-to-follow instructions on how to import PST to Thunderbird. Our focus will be on converting Outlook PST to Thunderbird's MBOX format.

Comparison of Outlook and Thunderbird

Outlook's Integration with Microsoft Suite: Outlook is deeply integrated with the Microsoft Office Suite, offering enhanced compatibility with Office applications like Word, Excel, and SharePoint. This integration is beneficial for users who rely heavily on other Microsoft products for their work.

Thunderbird's Customizability and Open-Source Nature: Unlike Outlook, Thunderbird is an open-source platform, which allows for greater customization. Users can modify its source code to better suit their needs or use various add-ons available in the Mozilla community. This flexibility is a significant advantage for users seeking a more personalized email experience.

Why PST to Thunderbird?

MS Outlook and Thunderbird are both prominent platforms for email management, but they differ substantially in their features, user interfaces, and pricing models. Outlook is a part of the paid Microsoft Office Suite, while Thunderbird is a free, open-source platform. They also store data in distinct file formats: Outlook uses PST files, and Thunderbird utilizes MBOX files.

The need to import PST to Thunderbird could arise from a variety of scenarios. One such scenario could be a job change where the new organization uses Thunderbird instead of Outlook. Alternatively, personal users might simply prefer the straightforward and user-friendly interface of Thunderbird. This need to transition across platforms requires PST to MBOX conversion. With this conversion, users can smoothly access their Outlook data in Mozilla Thunderbird.

Common Challenges in PST to Thunderbird Migration

Large File Handling: Migrating large PST files can be challenging due to size limitations and potential data corruption. It's crucial to break down large PST files into smaller chunks to ensure a smoother migration process.

Nested Folders and Attachments: Keeping the original folder structure and ensuring all attachments are correctly imported can be tricky. Users should verify the integrity of the folder hierarchy and attachments post-migration.

Data Safety and Backup Emphasis

Before you start the conversion process, it's crucial to back up your PST files. This step ensures that your data is safe in case of any unforeseen issues. Here's how to do it:

Locate your PST file: In Outlook, go to File > Account Settings > Account Settings. Under the Data Files tab, you'll see the location of your PST file.

Copy the PST file: Navigate to the PST file location in File Explorer. Right-click the PST file and select 'Copy.' Then, choose a secure location on your computer or an external drive and paste the copy there.

Verify the backup: Try to open the copied PST file in Outlook to ensure it's not corrupted and is a faithful copy of your original file.

Remember, having a backup can be a lifesaver in situations where data gets lost or corrupted during the conversion process.

How to import PST to Thunderbird?

There are multiple ways to import PST files to Thunderbird. These can be broadly categorized into manual methods and third-party PST to Thunderbird converter. This guide will walk you through both types. You can choose the method that best fits your comfort level and requirements.

Note: It's crucial to remember that before implementing any method, you should create a backup of your data. Backing up data protects you from the loss of valuable information due to unexpected errors or issues during the migration process.

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Quickly convert PST to MBOX. After conversion, open MBOX files with Thunderbird.

Method 1: Import PST to Thunderbird using the Default Program option

If you have both MS Outlook and Thunderbird installed on the same machine, this method is probably the easiest way to import PST files to Thunderbird. However, this method has its limitations, as it might not work perfectly with certain versions of the email clients.

  1. Go to the Settings and select the Default Program option
  2. Click on the Email and select Outlook (Desktop) from the Choose an app list
  3. Start Thunderbird and click on the Hamburger icon
  4. Select Tools and choose the Import option
  5. Select Import Everything or choose the Mail option as per your requirement and click on the Next button
  6. From the select the type of file, select Outlook and click on the Next button
  7. Click on the Finish button to complete the process.

Method 2: Import PST file to Thunderbird using Google Takeout

Google Takeout is another excellent tool that can help you to import PST to Thunderbird for free. This method involves configuring Gmail in Outlook, transferring emails from Outlook to Gmail, and then using Google Takeout to complete the migration process. This method might seem a bit lengthy and intricate as it is divided into six steps, but it's quite effective.

Step 1: Enable IMAP protocol from Gmail

  1. Sign in to your Gmail account, click on the Setting icon and select the Settings option
  2. Go to the Forwarding and POP/IMAP tab
  3. Enable IMAP and click on the Save Changes button.

Step 2: Allow less secure apps

  1. Go to the
  2. Select Security from the left sidebar and select the Less secure app access
  3. Enable Less secure app access option

Step 3: Configure Gmail in Outlook

  1. Start MS Outlook and go to the File menu
  2. Click on the Account Settings and select the Account Settings option
  3. Under the E-mail, click on the New
  4. Enter Name, Gmail address, password, re-type password and click on the Next button
  5. Once the verification process is complete, click on the Finish button.

Step 4: Migrate emails from Outlook to Gmail

  1. Select Gmail mailbox in Outlook and right-click on the selected mailbox
  2. Select the New Folder option and enter a folder name
  3. Select the Outlook emails you want to import and move selected emails to the folder that you created earlier
  4. Go to Gmail and refresh the page, and you will find emails moved to your Gmail accounts.

Step 5: Export emails from Gmail using Google Takeout

  1. Sign in to your Gmail account, open a new browser tab, and open Google Takeout (
  2. From Create a new export, select the Deselect all option.
  3. Select Gmail and click on the Next Step button.
  4. In the Choose file type, frequency & destination, choose Export once as frequency.
  5. Select the file type as .zip and choose the file size split option as per your requirement
  6. Click on the Create export button.
  7. Once your data is ready for export, you will receive an email.
  8. After receiving the email, click on the download link to start downloading the exported data.

Step 6: Import MBOX to Thunderbird

  1. Unzip the folder you downloaded
  2. Start Thunderbird, click on the hamburger icon and select the Add-ons option.
  3. Find ImportExportTools NG and click on the Add to Thunderbird button
  4. A popup will ask for permission, click on the Add button, and restart Thunderbird
  5. Right-click on the Local Folder and select the New Folder option
  6. Enter a folder name and click on the Create Folder button
  7. Right-click on the folder you just created and select the ImportExportTools NG option
  8. Select the Import MBOX file option, choose Import directly one or more MBOX files, and click on the OK button
  9. Go to the Unzip Folder and Select MBOX File and Click on Open Button
  10. Once the process is complete, click on the Finish button.

With the help of these manual solutions, you can import PST to Thunderbird for free. However, these methods are long and require technical expertise to perform. If you are looking for a quick solution, you can use a third-party PST File Converter.

Method 3: Convert PST to Thunderbird using PST to Thunderbird Converter

For those who are looking for a more straightforward and efficient way of converting their PST files to Thunderbird, using a PST to Thunderbird Converter, like the SysCurve PST File Converter, can be an ideal choice. This tool can convert PST files to multiple file formats, including MBOX, EML, EMLX, MSG, and others. By converting PST files to these formats, users can access their data not only in Thunderbird but also in other email clients like Eudora, Apple Mail, etc.

  1. Download and install the SysCurve PST File Converter
  2. Open the tool and click on the Add file option.
  3. Select PST file and click on the OK button.
  4. After the loading process, the software will generate preview mode inside the software window. You can select any message to view the message.
  5. Click on the Export option and select folders you want to convert.
  6. Select MBOX as an Export option and provide a path to save the MBOX files
  7. Click on the Export button to start the conversion process.
  8. Once the process is complete, click on the Finish button.

Other helpful features

SysCurve PST to Thunderbird Converter is not just a simple conversion tool. It is packed with numerous other features that will help you. Here are some of its features:

  • Convert PST to MBOX, EML, MSG, EMLX, HTML, RTF, and other file formats.
  • Preview all PST file data
  • Support large-size PST files
  • Maintain original folder structure
  • Migrate PST to Office 365 and Live Exchange server.
  • Free PST to Thunderbird conversion of the first 20 items from each folder
  • Support all versions of MS Outlook, including Outlook 2019 and 2016.
  • Compatible with all editions of Windows OS, including Windows 10


Even with clear instructions, sometimes things don't go as planned. Here's how to handle some common issues you might encounter during the PST to Thunderbird import process:

Thunderbird doesn't recognize the imported MBOX file

  1. Ensure that Thunderbird is updated to the latest version.
  2. Check if the MBOX file is not corrupted. If it is, you may need to repair it using a file repair tool.
  3. Try using the ImportExportTools NG add-on in Thunderbird again, ensuring you've followed all steps correctly.

Issues with Email Formatting in Thunderbird

  1. If the emails look jumbled or the formatting is off, it might be due to compatibility issues between Outlook and Thunderbird.
  2. Ensure that the conversion process from PST to MBOX or EML was completed without errors.

Frequently Asked Questions

How to import PST to Thunderbird without Outlook?

If you do not have access to Outlook, you can still import PST files to Thunderbird using the SysCurve PST file converter tool. This software efficiently converts PST to MBOX format, which can be easily imported into Thunderbird.

How to convert PST to MBOX for free?

While there are free manual methods to convert PST to MBOX, these methods can be quite time-consuming and require a certain level of technical knowledge. If you're dealing with a small number of PST files, you can use the free demo version of the SysCurve PST to Thunderbird Converter tool.

How to deal with large PST files when importing to Thunderbird?

When dealing with large PST files, it is recommended to use a third-party tool like SysCurve PST to Thunderbird Converter. This software can handle large PST files, unlike manual methods that often struggle with large volumes of data.

Can I import multiple PST files into Thunderbird at once?

Yes, using the SysCurve PST to MBOX Converter, you can import multiple PST files at once. This bulk conversion feature saves time and effort when dealing with numerous PST files.

How long does it take to import PST to Thunderbird?

The duration of the import process depends on several factors, including the size of the PST files, the performance of your computer, and the method you are using for the conversion. Manual methods typically take longer than third-party tools.

Will my data remain safe during the PST to Thunderbird import process?

Yes, provided you follow the recommended steps and use trusted tools. If using a third-party tool, ensure it is from a reputable source and has positive user reviews. Always backup your data before initiating the import process to avoid any potential data loss.

Are there any specific system requirements to import PST to Thunderbird?

The system requirements largely depend on the software you're using for the import. For instance, the SysCurve PST to Thunderbird converter tool is compatible with all editions of the Windows operating system, including the latest Windows 10. Ensure you have a computer with sufficient storage and processing power to handle the conversion process, especially if you're dealing with large PST files.

What are the differences between the manual methods and using a converter tool?

Manual methods often require more time and technical know-how but are usually free. Converter tools, on the other hand, offer a more straightforward process, often with additional features like handling large files, batch conversion, and repair of corrupted files, but they may come with a cost.

Can I convert specific emails from a PST file rather than the entire file?

Yes, with converter tools like SysCurve PST to Thunderbird Converter, you can select specific emails for conversion instead of the entire PST file. This selective conversion is beneficial if you only need specific data.

Are there any risks of data loss when using manual methods?

While manual methods are generally safe, there's always a minimal risk of data loss, especially if steps are not followed correctly or if there are unforeseen errors. Therefore, it's crucial to back up your PST files before starting the conversion process.

How can I ensure my converted emails maintain their original formatting in Thunderbird?

Most conversion tools aim to maintain the original formatting. However, it's advisable to check a few converted emails in Thunderbird to ensure the formatting is intact.

The Final Word

Migrating from one email client to another, especially when dealing with a large volume of data, can seem like a daunting task. But with the right knowledge and tools, it can be a smooth process. Whether you choose to use a manual method or the SysCurve PST to Thunderbird Converter tool, the key is to choose the one that suits your comfort level, technical expertise, and the size of the PST files you're dealing with. Always remember to backup your data before beginning the conversion or migration process.

Now, with all the information and guidance provided in this post, you can successfully import PST to Thunderbird.

The Author

Deepak Singh Bisht

Deepak Singh Bisht

Content Lead |

Deepak Singh Bisht is a dedicated IT professional with over 9 years of experience, is a key member at SysCurve Software for the last 5 years. His expertise lies in email migration and data recovery, with a focus on technologies like MS Outlook and Office 365. Deepak, who also delves into front-end technology and software development, holds a Bachelor's degree in Computer Applications.

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