ImportExportTools NG is a free, open-source Thunderbird add-on maintained on GitHub and is compatible with Thunderbird 78 and later versions. It is widely used for importing and exporting MBOX file in the email client. As per Mozilla Add-ons repository, there are more than 1 million active users of this add-on.
This Thunderbird add-on helps the users to import or export mailbox items, such as messages, profiles, and folders to MBOX and other formats, including EML, HTML, PDF, CSV, and plaintext. It can also come in handy when exporting mailbox items to MBOX format for backup and migration purposes.
However, there have been reports by some users that their ImportExportTools NG add-on is not working. As a result, they can’t export or import the MBOX files or view EML files in the email client.
In this guide, we will explain some tried and tested solutions to fix the Thunderbird ImportExport tools NG is not working issue and helps you import/export the MBOX files in Thunderbird.
If this add-on is not showing in the contextual menu, appearing greyed out, or failing to export/import the mail items, you can follow the below-given solutions to fix the issue.
Solution 1: Configure an Email Account in Thunderbird First
At times, when you install the ImportExportTools NG add-on in Thunderbird without configuring an email account beforehand, then you can’t use the ImportExportTools NG add-on to perform any import operations, as it is greyed out or not clickable. There is, however, an easy fix for it – add an email account in Thunderbird. Here’s how to configure a new account in Thunderbird:
- Open Thunderbird application.
- Click settings at the bottom left corner.
- Click Account Settings
- Click + New Account
- Click on Configure manually.
- Add the following account IMAP/POP details:
For Incoming Server
In case of IMAP:
Protocol: IMAP
Hostname: outlook.office365.com
Port: 993
Connection security: SSL/TLS
Authentication method: OAuth2
Username: your email ID
In case of POP3:
Protocol: POP3
Hostname: outlook.office365.com
Port: 995
Connection security: SSL/TLS
Authentication method: OAuth2
Username: your email ID
Outgoing Server
Hostname: smtp.office365.com
Port: 587
Connection security: STARTTLS
Authentication method: OAuth2
Username: your email ID
- Click on Done and follow the on-screen instructions to complete the process.
Solution 2: Reinstall the ImportExportTools NG Add-On
There are chances that the tool is not properly installed or the installation is damaged or corrupted. If this is the case, you can remove it and the install it again. Here’s how:
- Open Thunderbird app.
- Go to Tools > Add-ons and Themes.
- Find the ImportExportTools NG extension and click three dots. Choose Remove.
- Confirm and click Remove again.
- After removing the add-on, go to Tools > Add-ons and Themes and search for ImportExportTools NG.
- Click Add to Thunderbird.
- Click Add to confirm and install the add-on.
Once it is done, restart the email client and then try using the add-on to import or export Thunderbird mail items. This should resolve the ImportExportTools NG not working issue.
Solution 3: Verify the Version of the Thunderbird App Installed
A recent Thunderbird update can cause problems with the installed ImportExportTools NG add-on. This may lead to the add-on not working. You can check the version of the add-on in the “Version Compatibility” section on its page. You can also check this from the Help menu. Depending on the versions, you can either temporarily downgrade Thunderbird or reinstall the ImportExportTools NG add-on (See Solution 2 for this).
Here’s how to verify the version of Thunderbird:
- Open Thunderbird on your system.
- Open Thunderbird Menu using hamburger icon at the top.
- Click on Help > Troubleshooting Information.
- Check the version against the “Version” entry.
- Now, open Thunderbird Settings using the gear icon at the bottom left corner. Then click on Add-ons and Themes.
- Search for ImportExportTools NG using the search bar. Go to its official page and scroll down to the “Version Information” section to check the compatibility.
If you are using an older Thunderbird version, update it.
Note: As of Apr 2026, ImportExportTools NG ver14.1.18 supports Thunderbird v140-v151.
Solution 4: Disable Conflicting Add-ons in Thunderbird
Some particular Thunderbird add-ons – custom folder organizers, security scanners, and theme extensions may cause conflicts with ImportExportTools NG add-on. This happens when two or more add-ons try to control or modify the exact same application resources, files, or internal functions. For eg – An installed folder organizer tool may alter the context menu, which could hinder the functionality of ImportExportTools NG.
The solution is very straightforward – restart Thunderbird in safe mode and disable other add-ons. Then, enable them one by one. Doing this will help isolate the problematic add-on/s.
To eliminate conflicting add-ons in Thunderbird:
- Press and hold the ‘Shift‘ key.
- Click on the Thunderbird icon to launch it in safe mode.
- Open Thunderbird settings using the gear icon at the bottom. Click on Add-ons and Themes.
- Disable all other installed add-ons except for ImportExportTools NG using the toggle switch.
- Now, restart Thunderbird.
- If the ImportExportTools NG works, re-enable add-ons one at a time until it stops working again.
- Once you have found the problematic add-on, leave it disabled or check its developer page for a compatibility update.
Solution 5: Reset Thunderbird Profile
If the ImportexportTools NG not working issue is still there, what you can do now is recreate a new profile in Thunderbird. The reason for doing this is simple – a corrupted Thunderbird user profile can prevent add-ons from working properly.
Caution: Before proceeding, locate your Thunderbird profile folder and create a copy of the profile folder. This is because resetting will remove all its data – configured email accounts, local folders, custom mailbox folders, and settings permanently.
After doing this, follow the steps below:
- Now, Press Win + R to open Run.
- Type thunderbird.exe -ProfileManager and press Enter.
- Thunderbird Profile Manager window will appear. Click on Create Profile and enter a new profile name. Click Finish.
- Then select the newly created user profile from the list and click on Start Thunderbird.
- Thunderbird will start afresh and show the Account Setup window. Configure your account with the new profile and reinstall ImportExportTools NG.
- Test whether ImportExportTools NG now works.
Note: If ImportExportTools NG is working with no issues in the new profile, your original profile was corrupted.
Convert Thunderbird MBOX to PST using a Specialized Software
Tried all the above workarounds and still the ImportExportTools NG is not working? You can try switching email clients – migrate Thunderbird mailbox data to Windows Outlook. Unlike Thunderbird, which uses a third-party add-on for import/export purposes, Outlook is a reliable email client that has a native feature for this purpose.
You can do so by using the profile folder (.mbox file) stored at the default path on your system. But Outlook doesn’t natively support this file format. It only supports .pst file format. So, what you’d need is Stellar Converter for MBOX – a powerful MBOX to PST converter software that lets you save the mail items as an Outlook-importable PST file. Using this tool, you can also directly export them to an existing Outlook PST file or profile.
Highlights of this Stellar Converter for MBOX:
- Supports 17+ email clients: Mozilla Thunderbird, Apple Mail, Gmail (Takeout), etc.
- Find File simplifies locating MBOX/MBX/MBS/RGE files on the system or connected storage drive
- Shows enhanced preview of mailbox items to verify before saving
- Auto selects the path of the MBOX file for select email clients: Thunderbird, Spicebird, PocoMail, Netscape Mail, SeaMonkey, and Opera Mail
- Keeps the mailbox folder structure intact after converting MBOX to Outlook PST format
- Saves data as MSG and EML
Directly migrates mailboxes to Microsoft 365 (Technician edition only)
Why Consider Switching from Thunderbird to Outlook?
If the ImportExportTools NG add-on is repeatedly failing even after trying the above methods, consider switching from Thunderbird to Outlook on Windows. Outlook — particularly with a Microsoft 365 subscription — offers a powerful email management solution with built-in calendar integration, collaborative tools, and enterprise security features, for which, you need to install third-party add-ons in Thunderbird.
But as Outlook supports PST file format and not the MBOX file format – used by Thunderbird, you will need to first convert the MBOX file to PST format. For that, you can leverage Stellar Converter for MBOX. It can also help you quickly move to Outlook or Office 365. You can download the demo version to evaluate its capabilities.
Conclusion
In this blog, we have covered various stepwise methods to fix the ImportExportTools NG not working issue. But if you are still not able to use the add-on, you can try moving mailboxes from Thunderbird to Windows Outlook. For that, you’d need to convert MBOX to PST format using Stellar Converter for MBOX – a DIY software that can help you quickly convert MBOX to PST or migrate data to Outlook or Office 365 profile with 100% accuracy. You can download the demo version to evaluate its functionalities.
