How to open an Mbox file in Thunderbird or Apple Mail

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Mbox format

In CubeBackup, Gmail messages are exported as Mbox files, similar to exports from Google Takeout. An Mbox file stores multiple email messages in a single file and can be imported into email clients such as Mozilla Thunderbird and Apple Mail.

Open an Mbox file in Mozilla Thunderbird

The following instructions apply to Thunderbird on Windows and macOS, and are based on Thunderbird version 153.*.

Step 1. Install and set up Thunderbird

1. Download Thunderbird Desktop and install it using the default options.
2. Open Thunderbird. If this is your first time using Thunderbird, add an email account when prompted. Thunderbird requires at least one authorized account to be configured before you can import messages into Local Folders.
3. If you do not need to sync the emails to your mail server, select POP3 instead of IMAP to skip authorization use an empty personal account to avoid importing unnecessary messages.

Note: The configured account is only needed during the import and can be removed afterward. Removing the account does not remove messages imported into Local Folders unless you explicitly delete those local folders.

Step 2. Install ImportExportTools NG

1. Click the application menu icon in the upper-right corner of Thunderbird and select Add-ons and Themes.
2. Search for ImportExportTools NG.
3. Click + Add to Thunderbird, then confirm the installation.
4. Return to the main Mail tab.

Step 3. Create a local folder

1. In the left sidebar, right-click Local Folders and select New Folder ….
2. Enter a descriptive name, such as CubeBackup imported email, and click Create Folder.

Step 4. Import the Mbox file

1. Right-click the local folder you created.
2. Select ImportExportTools NG > Import mbox Files > Individual mbox Files.
3. Find and select the CubeBackup Mbox file, then click Open.
4. Wait for the import to finish. Select the imported folder in the sidebar to view and search the messages.

Import EML messages to Outlook Mail

After importing the mbox files in Thunderbird, you can follow the steps below to proceed:

Step 1. Export Gmail messages to EML files (optional)

1. Right-click the local folder you created in Thunderbird.
2. Select ImportExportTools NG > Export All Messages In Folder > EML Message Format > Messages And HTML Index.
3. Select the target folder and wait for the export to complete.

Step 2. Open EML files in MS Outlook

Importing EML files into Outlook is pretty easy:

• [Optional] Create a folder in MS Outlook to contain the email messages, then select it to make it the active folder.
• Go to the local directory where the EML files are stored and drag & drop them into Outlook .

Note: If you have a large number of messages, this operation could take a long time.

Open an Mbox file in Apple Mail (macOS only)

Apple Mail supports the Mbox format directly, so no add-on or format conversion is required.

1. Open the Mail app on your Mac.
2. From the menu bar, select File > Import Mailboxes.
3. Select Files in mbox format, then click Continue.
4. Find and select your CubeBackup Mbox file, then click Choose.
5. Wait for the import to complete.
6. In the Mail sidebar, open the new Import mailbox to view the messages. You can drag the imported mailbox or its messages to another mailbox if you want to reorganize them.

Note: If Import is not visible in the sidebar, select View > Show Sidebar. Importing a large Mbox file may take some time, and Mail may need additional time to index the messages for search.