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Import .mbox files to Google Workspace (formerly G Suite / Google Apps)

This script allows Google Workspace admins to import mbox files in bulk for their users.

DISCLAIMER: This is not an official Google product.

If you want to migrate from Mozilla Thunderbird, try mail-importer.

You only authorize it once using a service account, and then it can import mail into the mailboxes of all users in your domain.

A. Creating and authorizing a service account for Gmail API

  1. Go to the Developers Console and log in as a domain super administrator.

  2. Create a new project.

  • If you have not used the API console before, select Create a project from the Select a project dropdown list.
  • If this is not your first project, use the Create Project button.
  1. Enter "Gmail API" (or any name you prefer) as the project name and press the Create button. If this is your first project you must agree to the Terms of Service at this point.

  2. Click the Enable and manage APIs link in the Use Google APIs box.

  3. Enable the Gmail API - Select the Gmail API link and press the Enable API button. You can leave the default APIs enabled - it doesn't matter.

  4. Click the 3-line icon () in the top left corner of the console.

  5. Click IAM & Admin and select Service accounts.

  6. Click Create service account.

  7. Enter a name (for example, "import-mailbox") in the Name field.

  8. Check the Furnish a new private key box and ensure the key type is set to JSON.

  9. Check the Enable G Suite Domain-wide Delegation box and enter a name in the Product name for the consent screen field.

  10. Click Create. You will see a confirmation message advising that the Service account JSON file has been downloaded to your computer. Make a note of the location and name of this file. This JSON file contains a private key that potentially allows access to all users in your domain. Protect it like you'd protect your admin password. Don't share it with anyone.

  11. Click Close.

  12. Click the View Client ID link in the Options column.

  13. Copy the Client ID value. You will need this later.

  14. Go to the Domain-wide Delegation page of the Admin console for your Google Workspace domain.

  15. Under Client ID, enter the Client ID collected in step 15.

  16. Under OAuth Scopes, enter the following:,
  1. Click Authorize.

You can now use the JSON file to authorize programs to access the Gmail API "insert" and "label" scopes of all users in your Google Workspace domain.

B. Importing mbox files using

Important: If you're planning to import mail from Apple, see the notes below.

  1. Download the script -

  2. Download and install Python 2.7 (not Python 3.x) for your operating system if needed.

  3. Open a Command Prompt (CMD) window (on Windows) / Terminal window (on Linux).

  4. Install the Google API Client Libraries for Python and their dependencies by running, all in one line:


    sudo pip install --upgrade google-api-python-client PyOpenSSL


    C:\Python27\Scripts\pip install --upgrade google-api-python-client PyOpenSSL

    Note: On Windows, you may need to do this on a Command Prompt window that was run as Administrator.

  5. Create a folder for the mbox files, for example C:\mbox.

  6. Under that folder, create a folder for each of the users into which you intend to import the mbox files. The folder names should be the users' full email addresses.

  7. Into each of the folders, copy the mbox files for that user. Make sure the file name format is <LabelName>.mbox. For example, if you want the messages to go into a label called "Imported messages", name the file "Imported messages.mbox".

Your final folder and file structure should look like this (for example):

C:\mbox\\Imported messages.mbox
C:\mbox\\Other imported messages.mbox
C:\mbox\\Imported messages.mbox
C:\mbox\\Other imported messages.mbox

IMPORTANT: It's essential to test the migration before migrating into the real users' mailboxes. First, migrate the mbox files into a test user, to make sure the messages are imported correctly.

  1. To start the migration, run the following command (one line):


    python --json Credentials.json --dir C:\mbox


    C:\Python27\python --json Credentials.json --dir C:\mbox
  • Replace with the full path of - usually ~/Downloads/ on Mac/Linux or %USERPROFILE%\Downloads\ on Windows.
  • Replace Credentials.json with the path to the JSON file from step 12 above.
  • Replace C:\mbox with the path to the folder you created in step 5.

The mbox files will now be imported, one by one, into the users' mailboxes. You can monitor the migration by looking at the output, and inspect errors by viewing the import-mailbox-to-gmail.log file.

Options and notes

  • Use the --from_message parameter to start the upload from a particular message. This allows you to resume an upload if the process previously stopped. (Affects all users and all mbox files)

    e.g. ./ --from_message 74336

  • If any of the folders have a ".mbox" extension, it will be dropped when creating the label for it in Gmail.

  • To import mail from Apple, make sure you export it first - the raw Apple Mail files can't be imported. You can export a folder by right clicking it in Apple Mail and choosing "Export Mailbox".

  • This script can import nested folders. In order to do so, it is necessary to preserve the email folders' hierarchy when exporting them as mbox files. In Apple, this can be done by expanding all subfolders, selecting both parents and subfolders at the same time, and exporting them by right clicking the selection and choosing "Export Mailbox".

  • If any of the folders have a ".mbox" extension and a file named "mbox" in them, the contents of the "mbox" file will be imported to the label named as the folder. This is how Apple Mail exports are structured.

  • To run under Docker:

    1. Build the image:
     docker build -t google/import-mailbox-to-gmail .
    1. Run the import command:
     docker run --rm -it \
         -v "/local/path/to/auth.json:/auth.json" \
         -v "/local/path/to/mbox:/mbox" \
         google/import-mailbox-to-gmail --json "/auth.json" --dir "/mbox"

    Note -v is mounting a local file/directory /local/path/to/auth.json in the container as /auth.json. The command is then using it within the container --json "/auth.json". For more help, see Volume in Docker Run.