blog / Email Migration / 4 Verified Solution to Import MBOX to Thunderbird in 2026

4 Verified Solution to Import MBOX to Thunderbird in 2026

By / Email Migration / Updated on: February 10, 2026 / Read time: 9 min

In this blog, we’ll discuss methods to import MBOX files to Thunderbird. If you’re one of those who had an MBOX file but don’t have its parental email client and want to export MBOX files to Mozilla Thunderbird, then you’re on the right blog.

MBOX file format is the most extensively used file format. It is supported and generated by more than 20 email clients. Sometimes users get stuck in a situation where they have MBOX files and want to import them to see their data. In this scenario, Mozilla Thunderbird is a widely preferred email client because it is a free, open-source email application and compatible with both Windows and Mac Operating Systems. So, now the question arises how to import MBOX files to Thunderbird?

Methods to Import MBOX files to Thunderbird Mail

Mozilla Thunderbird is a versatile email client that natively supports MBOX and MSF file types. You can import your data using two primary methods—neither of which requires complex file conversions:

  • The Add-on Method: Use the ImportExportTools NG extension to automate the process, making it the easiest choice for most users.
  • The Manual Method: Copy and paste MBOX files directly into the Local Folders directory within your Thunderbird profile.

Both approaches preserve your original emails, attachments, and folder structures perfectly. This makes Thunderbird an excellent, free solution for accessing archives like Google Takeout.

Method 1: Import MBOX to Thunderbird Via ImportExportTools NG

Importing MBOX files into Thunderbird can be quite challenging if you do not have the right resources. The good news is that Thunderbird’s ImportExportTools NG add-on makes it easy to handle MBOX files. In case you need to do some emailing client work or need to do some emailing organizing, this tutorial will cover the steps to take to get MBOX files into Thunderbird using ImportExportTools NG.

What is ImportExportTools NG?

The ImportExportTools NG add-on is used to import and export MBOX and other emailing files, to and from, Mozilla Thunderbird. It is the improved version of the original ImportExportTools and is specifically for the more recent versions of Thunderbird. This tool provides the ability to import emails of various formats (EML, MBOX, and Maildir) into Thunderbird, and simplifies the backup process for data within Thunderbird.

Follow below Steps to Import MBOX Files to Thunderbird

Step 1: Install ImportExportTools NG Extension

Before starting the import process, you need to install the ImportExportTools NG extension in Thunderbird.

  1. Open Thunderbird and click on the menu icon (three horizontal lines) in the top-right corner.
  2. Select Add-ons and Themes.
  3. In the search bar, type ImportExportTools NG and press Enter.
  4. Click on Install next to the ImportExportTools NG extension.
  5. After installation, restart Thunderbird to activate the extension.

Step 2: Prepare MBOX Files

Make sure you have your MBOX files ready. MBOX is a standard format for storing email messages, and they usually have an extension of .mbox. You can get MBOX files from different email clients, email archives, or even backups.

Step-3: Open Thunderbird and Go to the MBOX Import Option

Once ImportExportTools NG is installed, you’ll need to access the import option to start the process.

  1. Open Thunderbird and go to the folder where you want to import the MBOX file. This could be an existing folder or a new folder you create for the imported emails.
  2. Right-click on the folder and select ImportExportTools NG from the context menu.
  3. Choose Import MBOX file.

Step 4: Select Your MBOX File

A file explorer window will appear, allowing you to select the MBOX file you want to import.

  1. Browse through your computer’s directories to locate the MBOX file.
  2. Select the file and click Open.

Step 5: Choose Import Settings

Once you’ve selected the MBOX file, you’ll be given different options for importing:

  • Import directly one MBOX file: This will directly import the selected MBOX file into Thunderbird.
  • Import all messages from a MBOX file: If you want all the emails within the MBOX file to be imported, select this option.
  • Import a MBOX file into a new folder: This allows you to import the MBOX file into a new folder within Thunderbird.

Select the option that fits your needs and click OK to proceed.

Step-6: Wait for the Import Process to Complete

Thunderbird will now import the MBOX file into the selected folder. Depending on the size of the MBOX file, this process may take a few minutes.

Once the import is complete, you’ll see the emails from the MBOX file in the folder you selected.

Step 7: Check the Imported Emails

After the import, navigate to the folder where the emails were imported. You should see all the emails neatly arranged in Thunderbird. You can now manage, organize, and access your old emails just like any other email within Thunderbird.

How ImportExportTools NG Helps

  • Fast and Easy Importing: The tool makes importing MBOX files into Thunderbird incredibly simple and fast. No more hassle with complicated manual methods.
  • Supports Multiple Formats: Besides MBOX, the extension supports other formats like EML and Maildir, making it versatile for various email backups.
  • Bulk Importing: You can import several MBOX files at once, which saves you time if you have multiple backup files.
  • Preserves Folder Structure: The tool ensures that the folder structure from your MBOX files is preserved, keeping your emails organized.

Method 2: The “Manual Move” Method (No Add-ons Required)

Because Thunderbird stores its mail in MBOX format, you can manually place your file into its profile folder.

Process:

  1. Close Thunderbird.
  2. Locate your Thunderbird Profile folder (usually in %AppData%\Thunderbird\Profiles\[your-profile]\Mail\Local Folders).
  3. Copy your MBOX file and paste it into the Local Folders directory.
  4. Crucial Step: Ensure the file has no file extension (e.g., rename Inbox.mbox to just Inbox).
  5. Restart Thunderbird; the folder will appear under Local Folders.

Pros: Completely native; no software or add-ons needed.

Method 3: Native “Import” Tool (Thunderbird 102+)

Modern versions of Thunderbird have a built-in import wizard that can sometimes handle MBOX data if it is part of a backup or specific export.

Process:

  1. Go to Tools > Import.
  2. Select Import from a file.
  3. Select Import backup profile or Import messages (depending on your version).

Pros: No installation needed.

Cons: Often expects a specific folder structure (like a ZIP from Google Takeout) rather than a single standalone .mbox file.

Method 4: The “Feed Account” Workaround (Preview Without Importing)

If you want to view the emails without actually merging them into your main database, you can use the Feed account trick.

Process:

  1. Create a new Feed Account in Thunderbird (File > New > Feed Account).
  2. Go to Account Settings for that Feed.
  3. Under Server Settings, change the Local Directory to the folder on your computer that contains your MBOX files.
  4. Restart Thunderbird; the MBOX files in that folder will show up as folders in the Feed account.

Pros: Great for viewing large archives without bloating your main profile.

Method 5: Importing Emails from Gmail to Thunderbird:

In this manual method, users have to configure the Thunderbird with the Gmail account. Hence, to pursue this method, users need a Gmail account.

There are three phases in this method which go as follows:

Step 1: Enable the IMAP option 

  • Log in to your Gmail account.
  • Secondly, go to the Setting option and click on the More Settings from the list.
  • Now go to the Forwarding and POP/IMAP option and enable the IMAP

Step 2: Configure Thunderbird Manually (Optional)

  • Firstly, launch Thunderbird on your system.
  • Secondly, enter the login credentials and open your Thunderbird account.
  • Now, check the IMAP (remote folders) option and click on the manual configure
  • Enter the required information, as given below:
 I/OServerHostnamePortSSLAuthentication
IncomingIMAPimap.gmail.com993(SSL) or 143SSL/TLS0Auth2
OutgoingSMTPSmtp.gmail.com25(SSL) or 465SSL/TLS0Auth2

Incoming: imap.gmail.com/ port: Either 993(SSL) or 143(very infrequently 580)

Outgoing: smtp.gmail.com/ port: Either 25(SSL) or 465(very infrequently 2525) 

  • After this, click on the Re-test.
  • If the provided information is correct, then the task will finish.
  • Now make a click on the Create a New Account.
  • Then verify the Gmail account from Thunderbird.
  • After that, drag and drop the MBOX file into the Gmail inbox.

Step 3: Run the Thunderbird Auto-Configuration

  1. Open Thunderbird. (If it’s a fresh install, the “Set Up Your Existing Email Address” page will open automatically).
  2. If you already have Thunderbird open, go to: Menu (three lines) > Account Settings > Account Actions > Add Mail Account.
  3. Enter your details:
    • Your full name: How you want your name to appear on sent emails.
    • Email address: Your full @gmail.com address.
    • Password: Your regular Gmail password.
  4. Check the Remember password box.
  5. Click Continue.

Step 4: The Authentication Bridge

  1. Thunderbird will search for settings and should show: “IMAP (remote folders)”.
  2. Click Done.
  3. A Google Login popup window will appear (this is the OAuth2 process).
  4. Enter your email and password in this Google window.
  5. If you have Two-Factor Authentication (2FA) enabled, enter your code or tap “Yes” on your phone.
  6. Click Allow to give Thunderbird permission to access your emails and calendar.

Common Error while Configure a Email Account in Thunderbird

  • “Could not verify password”: This usually happens if cookies are disabled in Thunderbird. Go to Settings > Privacy & Security > Web Content and ensure “Accept cookies from sites” is checked.
  • App Passwords: If you are using an extremely old version of Thunderbird that doesn’t support the Google popup, you would need to generate an “App Password” in your Google Account security settings—but for modern versions (102 or higher), the standard password is best.

Wrapping Up:

Importing MBOX files to Thunderbird is a straightforward task with the help of the ImportExportTools NG extension. Whether you need to restore old emails or migrate data from another email client, this extension simplifies the process. With just a few clicks, you can have your MBOX files fully integrated into Thunderbird and ready to go.

To get started with Import MBOX to Thunderbird, follow the steps above, and enjoy seamless email management with Thunderbird.

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