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How to open an Mbox file in Microsoft Outlook.

Mbox format

In CubeBackup, Gmail messages are exported as Mbox files (similar to Google Takeout exports). The Mbox format can be opened by Apple Mail and other mail clients, but unfortunately, Microsoft Outlook cannot open Mbox files directly on Windows.

One way around this is to use another mail client, like Thunderbird, to convert Mbox files to a format compatible with Microsoft Outlook.

Open the Mbox file in Outlook

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.

Step 5. 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 6. 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.