Import your MBOX into Thunderbird.

Documentation checked 9 September 2026 · Desktop Thunderbird

For a lasting mailbox in a desktop app, use Thunderbird with the ImportExportTools NG add-on. If you just need to look up an email or retrieve a file, you can open the MBOX in your browser without installing Thunderbird. MBOX Lens’s workspace clears when you close or reload the page; an import into Thunderbird stays in its local storage.

1. Prepare the MBOX and keep the original.

   Extract a downloaded ZIP first, then locate the MBOX file inside. For a Gmail export, follow our Google Takeout guide. Keep an unchanged copy of the export. If Thunderbird already holds important mail, follow its profile backup instructions before importing.

2. Install ImportExportTools NG.

   Open Thunderbird’s Add-ons Manager, choose Extensions and search for ImportExportTools NG. Install it and restart Thunderbird if prompted. Mozilla’s add-on installation guide explains this process. Check the add-on’s current compatibility listing for your Thunderbird version; menu names can differ by version, language and operating system.

3. Choose Local Folders.

   In Thunderbird’s folder pane, select Local Folders. This is the destination for the add-on’s MBOX import. You do not need to reconnect the email account that originally supplied the archive. If the folder list is filtered, switch it to the All folders view and look for Local Folders there.

4. Import the file from the folder menu.

   Right-click Local Folders, or Control-click on a Mac. Choose ImportExportTools NG → Import mbox Files → Individual mbox Files, then select your extracted MBOX. For an ordinary single-file export, use the individual-files option. The separate options mentioning sbd structure are for exports that include Thunderbird’s folder hierarchy. These choices are described in the add-on’s import menu help.

5. Check the imported mail.

   Let the import finish, then expand Local Folders and open the imported mailbox. Check several familiar subjects, dates, message bodies and attachments. Compare the message count with your source export if you have a known count. Keep the original even after the import succeeds; Thunderbird’s working copy is not a separate backup.

Why is the MBOX import option missing?

Confirm that the add-on is enabled and that you are opening the menu for Local Folders. Its documentation restricts MBOX imports to Local Folders; selecting a connected IMAP inbox can hide the option. Use the add-on’s folder menu for this procedure. If the menu still differs, check its current help and compatibility listing rather than repeatedly importing the same archive.

Will this put the messages back into Gmail?

This procedure imports into Thunderbird’s Local Folders. Uploading messages to a connected mailbox is a separate action. Copying them into an IMAP account’s folders can send them to that provider and use its storage; only do that if restoring mail online is your intention. Thunderbird explains the relationship in its IMAP synchronization guide.

Only need the attachments?

You can extract selected attachments in MBOX Lens without importing the mailbox into Thunderbird. Open the file, find the messages you need and review the files before downloading.

These steps are based on Thunderbird and ImportExportTools NG documentation, not a hands-on test of every version or export format. Thunderbird and the add-on are independent of MBOX Lens.