Restore Gmail messages from a Google Takeout MBOX backup

Downloading a Google Takeout archive and restoring it are different operations. Gmail does not offer a button that uploads a Takeout ZIP and rebuilds the mailbox. The route below uses Thunderbird to read the saved messages and an IMAP connection to copy them to a Gmail account you can access.

You do not need PST or the MBOX to PST converter for this direction of transfer. If your destination is Outlook instead, use the Takeout-to-PST guide.

Decide what you actually need to restore

Before uploading, search Gmail for a few messages you believe are missing. Archived mail may still exist in All Mail even though it is absent from Inbox. Uploading the same history again can create unwanted copies or make verification confusing.

Keep the original download and extracted MBOX files. Work with a copy and leave enough local space for Thunderbird's imported messages as well as the archive.

Open the saved mail in Thunderbird first

1. Extract all Takeout parts into separate folders so you can account for every MBOX without overwriting identically named files.

2. Install a version of ImportExportTools NG compatible with your Thunderbird release through Add-ons and Themes.

3. Create a folder under Local Folders, then use its context menu to open ImportExportTools NG → Import mbox Files and select your working MBOX. The exact submenu wording varies by add-on release. MBOX import belongs under Local Folders, not directly under an IMAP account; the add-on's documentation records that restriction.

Open several imported messages before connecting the destination. If dates, bodies, or attachments are already missing locally, stop and investigate the archive. Uploading will not repair absent source data.

Connect the destination Gmail account

Add the destination account through Thunderbird's account setup, choose IMAP, and complete Sign in with Google. Personal Gmail accounts do not need the old Enable IMAP switch. A managed Google Workspace account may have administrator restrictions. Follow Google's current mail-client guidance if authentication fails.

Check the address displayed in Thunderbird. It is easy to import into the original account when you intended a new one. Create a clearly named destination folder, such as Restored Takeout — September 2026, under that Gmail account; check that it is visible as a label in Gmail webmail.

Copy a test batch before the whole archive

Select a few messages in the imported Local Folders mailbox. Use Copy To to send them to the Gmail destination folder. Copying leaves the local source available while you check the server result.

Wait for activity to finish, then open Gmail in a browser. Search within the destination label and verify the chosen messages, dates, bodies, and attachments. Avoid judging by a conversation total alone: Gmail can group several messages into one conversation.

Once the test works, copy manageable batches and keep a simple record of which local folder and range you sent. If a batch stalls, identify the last verified group before retrying. There is no universal batch size or completion time: message sizes, connection quality, account storage, and service limits all matter.

Will the original Gmail labels return automatically?

Google saves label information in an X-Gmail-Labels message header in Takeout exports. That does not mean an ordinary IMAP upload will rebuild the same labels and assign them exactly as before. Treat the destination folder used for the upload as the organization you are deliberately creating. Google describes the saved label header here.

For example, if a message originally carried both Receipts and Travel, first restore one checked copy. Apply the desired labels in Gmail afterward if necessary. Uploading overlapping label exports into several destination folders without a plan makes duplicate checks harder. Do not delete supposed duplicates based only on matching subjects.

Troubleshoot a partial restoration

Contacts, calendars, filters, passwords, and account settings are outside this mail-only process. Keep those exports separate. When the transfer is finished, preserve the original Takeout backup and the batch record until you are satisfied that the destination contains what you intended.

Primary sources

• ImportExportTools NG: developer documentation
• Google: Gmail in another mail client
• Google: Takeout data and Gmail labels

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