How to Fix “Import MBOX File Greyed Out in Thunderbird”

Jamie Kaler Contribution

Rollins Duke Approved By

Published On June 18th, 2025 • 6 min read

When we are dealing with migrating files to other email clients, in some way or another. For Thunderbird users, the MBOX format is a common method for saving emails from the email client. However, there are some cases when users encounter with issue “Import MBOX Files Greyed Out Thunderbird”.

There are times when even after adding the Add-ons to Thunderbird, the Import option doesn’t work. Let’s find out how to resolve the issue without any complex procedure.

Table of Contents Hide

Understand MBOX Files and Thunderbird

Before we go deep into the solutions, let’s understand the MBOX files and how Thunderbird interacts with the files.

MBOX files are a common file format to store a collection of email messages. The files are plain text that have multiple emails concatenated into a single file. Each of these files is separated by a “From” line. It is one of the widely used file formats by various email clients.

Thunderbird is a popular free open-source email client developed by Mozilla. The email client supports MBOX format for importing and exporting emails effortlessly. the options to Import MBOX file option is not available directly for the user without the Add-ins.

Why is “Import MBOX files” Greyed Out in Thunderbird?

The reason why you might find the Import MBOX files option greyed out in Thunderbird is often due to misconfigurations within the client or the absence of any specific add-on. More importantly, Thunderbird by default does not have the built-in, direct MBOX import features. It relies on the extension that has this feature.

To get the “Import MBOX files” option, we need to get the “ImportExportTools NG” add-on. Without the Add-in, Thunderbird simply does not have the mechanism to recognise the process the import of importing MBOX files. Here, the options won’t be available if the add-on is installed and enabled, but rather greyed out.

Other common reasons why “Import MBOX Files Greyed Out Thunderbird”

Corrupt Thunderbird Profile: A Damaged user profile of Thunderbird can cause various errors, resulting in impaired functionality, including the import options. If you suspect that’s the cause, then get the solutions from here: “fix corrupt Thunderbird profile”.
Outdated Thunderbird: If you have an older version of Thunderbird, there is are chance of having issues with the latest add-on.
Incorrect File Permissions: Sometimes, the problem would be with the MBOX Files. Those files could restrict the “Thunderbird import mbox not working” issue.

The MBOX file you’re trying to import may have restricted permissions, preventing it from being imported.

Instant Solution:

How to Use the Add-on and Perform the Import Process?

The single answer to this is that it is easy to resolve the “Import MBOX files greyed out Thunderbird”. We need to install and properly utilise the “ImportExportTools NG” add-on.

Install and Use “ImportExportTools NG” Add-on.

Start Thunderbird Application.
Go to Tools>>Add-ons and Themes:
In the Add-on Manager, type “ImportExportTools NG” in the search bar and press Enter.
The result will display the “ImportExportTools NG” add-on.
Click on the “Add to Thunderbird” button.
Click on “Add” to confirm the installation.
Sometimes you might need to restart Thunderbird to enable the Add-on in the client.

How to Use the Import Options?

After restarting Thunderbird, the “Import MBOX files” option should appear in the options. Now, follow the steps of the import process.

Navigate to the folder where you want to import the MBOX emails.
Right-click the folder and go to “ImportExportTools NG”.
From the different options, select “Import MBOX files”.
Select from:
- Import directly one or more MBOX files.
- Import MBOX files from the directory.
Now, browse and select the MBOX files and click Open.
The Thunderbird will start importing the emails from the selected MBOX files.
Once, check the imported MBOX files.

For more details, visit: Open MBOX files in Thunderbird Account.

Fix “Import MBOX Files Greyed Out Thunderbird”

Now we know how the add-on works. Let’s find out why the Import MBOX file option gets greyed out or does not work properly even after installing the appropriate add-ons.

Check the Add-on Once

Before we move to any troubleshooting steps, first check the Add-on once again. Ensure that you have the add-on enabled if yes, try removing and installing.

Steps to remove the Add-on:

Open Thunderbird.
Navigate to Tools>Add-ons and Theme.
Go to the ImportExportTools NG.
Click on the Remove button.

Again, reinstall the Add-on and check whether the “Import MBOX file” option is working properly.

Update Thunderbird Application

The old version of Thunderbird is less likely direct cause of “import mbox files greyed out thunderbird”

How to check for updates: In Thunderbird, go to Help> About Thunderbird. Thunderbird will automatically check for updates. If the update is available, install it and restart Thunderbird.

Check Thunderbird Profile

Back up the Thunderbird Profile: Before we work on any profile-related work, always back up Thunderbird emails. It is crucial to prevent any data loss. To find the folder, go to Help> Troubleshooting Information, then click “Open Folder“.
Create New Profile: You can create a new Thunderbird profile and see if the import option is available after installing the ImportExportTools NG. To create a new Thunderbird profile:
- Open the profile by typing thunderbird.exe -P in the Run dialogue.
- Create a new profile and set it as the default.
Migrate the Data: If the new profile works, you might consider migrating the data from the old profile to the new one.

FAQs

Q) Why is “Import MBOX File” not showing in my Thunderbird?

A) The option only appears when you have the add-on “ImportExportTools NG”. Thunderbird does have built-in options to add MBOX files.

Q) Is “ImportExportTools NG” safe to use?

A) Yes. Since it is one of the commonly used add-ons in Thunderbird, it is only available on the official website.

Q) How to use the “ImportExportTools NG” add-on?

A) You can install the add-on into the Thunderbird application from the Add-ons Manager. After enabling the add-ons all the import export options will be available

Conclusion

When you want to import the MBOX files into the Thunderbird account, but can’t due to some reasons, the feature is disabled. While we are performing the transmission of the emails into the account, encountering the “Import MBOX Files Greyed Out Thunderbird” issue can be a minor setback. Here we have the complete details on how to perform the import process, and then the solution to why the Import MBOX file option is not working.