How to Open MBOX File: Read Your Gmail Takeout Export
An MBOX file is a whole mailbox in one file: usually your Gmail export from Google Takeout ("All mail Including Spam and Trash.mbox"), or mail from Apple Mail or Thunderbird. Apple Mail and Thunderbird can import it, but Outlook and Gmail can't. The free viewer below opens even multi-gigabyte MBOX files in your browser, shows your Gmail labels as folders, and lets you read messages, download attachments and save emails as .eml, without uploading anything.
Choose what you need
Open MBOX File Online: Browse a Gmail Takeout Export (Free)
Drop an .mbox file below, even a multi-gigabyte Google Takeout export. The viewer indexes every message, turns Gmail labels into folders, lists the emails by date with sender and subject, and opens any message so you can read it, download its attachments or save it as .eml.
Good to know: the file is read in 8 MB pieces, so large mailboxes work without loading everything into memory. Remote images in emails are blocked.
🔒 Nothing is uploaded — your mailbox never leaves this deviceOn this page
What is an MBOX file?
MBOX is a simple, decades-old format that stores many emails one after another in a single text file; each message starts with a line beginning with "From ". Each message inside is a normal email with headers, body and Base64-encoded attachments, which is why MBOX files are large. Unix mail systems, Thunderbird, Apple Mail exports and Google Takeout all use it.
| Full name | Mailbox (Unix mbox format) |
|---|---|
| Contains | Many emails with attachments, one after another |
| Gmail extras | An X-Gmail-Labels header with each message's labels |
| Related | .eml (one email), .pst (Outlook), .mbx |
How to open an MBOX file: quick answer
| Goal | Best option |
|---|---|
| Look through or search old Gmail | The viewer above (any device) |
| Keep it in a mail app on a Mac | Apple Mail: File > Import Mailboxes > Files in mbox format |
| Keep it in Thunderbird (Windows, Mac, Linux) | ImportExportTools NG add-on > Import mbox file |
| Put a few emails into Outlook or Gmail | Viewer above > Save as .eml, then open or drag them in |
Gmail Takeout MBOX files
When you export Gmail with Google Takeout you get a ZIP with a Mail folder containing All mail Including Spam and Trash.mbox (and sometimes one MBOX per label). Unzip it first, then:
- Drop the .mbox into the viewer above. It indexes the messages, even for files of several gigabytes, because it reads the file in pieces.
- Your Gmail labels (Inbox, Sent, Important, your own labels) appear as folders, with message counts.
- Open any email to read it, download attachments, or save it as .eml.
Import an MBOX into Apple Mail or Thunderbird
Apple Mail (Mac)
- Choose File > Import Mailboxes.
- Select Files in mbox format and click Continue.
- Pick the folder that contains the .mbox. The messages appear under On My Mac > Import.
Thunderbird (free, Windows, Mac, Linux)
Install the ImportExportTools NG add-on (Tools > Add-ons and Themes), then right-click a local folder > ImportExportTools NG > Import mbox file. Thunderbird keeps local folders in mbox format itself, so imports are fast and faithful.
MBOX and Outlook
Outlook can't import MBOX files. Your options:
- For a handful of messages: save them as .eml with the viewer above and open or drag them into Outlook.
- For a whole mailbox: import the MBOX into Thunderbird, connect the destination account (Outlook.com, Microsoft 365, Gmail) in Thunderbird via IMAP, and drag the folders across. The messages upload to the server and appear in Outlook.
- Commercial MBOX-to-PST converters exist if you need a PST file.
MBOX problems and fixes
The file is too big for my apps
Takeout MBOX files are often 5–50 GB. The viewer above handles large files because it never loads the whole file at once; mail apps may need a lot of time and disk space to import them.
Some messages look merged or split
Some exports don't escape lines starting with "From " inside messages, which can confuse readers. The viewer only treats "From " lines that look like real separators (with a date) as new messages.
The download is a .zip or .tgz
Extract it first; the .mbox is inside the Mail folder.
It opens as text
That's normal for MBOX: it's plain text. Use the viewer or a mail app to see the messages properly.
Sources and technical references
- RFC 4155: The application/mbox Media Type — IETF
- Google Takeout: import an MBOX file with Apple Mail — Swarthmore College ITS
- ImportExportTools NG for Thunderbird — Thunderbird Add-ons
- Google Takeout — Google
Frequently asked questions
How do I open an MBOX file?
Drop it into the free viewer on this page: it lists every message, shows Gmail labels as folders and opens any email with its attachments, all in your browser. To keep the mail in an app, import it into Apple Mail or Thunderbird.
How do I open a Gmail Takeout MBOX file?
Unzip the Takeout download and find All mail Including Spam and Trash.mbox in the Mail folder. Drop it into the viewer on this page to browse it by label, or import it into Apple Mail or Thunderbird.
Can Outlook open MBOX files?
No, Outlook can't import MBOX. Save the messages you need as .eml with the viewer here and open them in Outlook, or import the MBOX into Thunderbird and drag the folders into an Outlook.com or Microsoft 365 account connected by IMAP.
How do I import an MBOX file into Apple Mail?
In Mail choose File > Import Mailboxes, select Files in mbox format, click Continue and choose the folder that contains the .mbox. The messages appear in an Import mailbox under On My Mac.
How do I import an MBOX into Thunderbird?
Install the free ImportExportTools NG add-on, right-click a local folder and choose ImportExportTools NG > Import mbox file. Thunderbird stores local folders in mbox format, so the import keeps the messages intact.
Can I put an MBOX back into Gmail?
Gmail has no MBOX import. Import the file into Thunderbird or Apple Mail, add your Gmail account by IMAP in the same app, and drag the messages into a Gmail label; they upload to your account.
Why is my MBOX file so large?
An MBOX stores every email and attachment as text, and attachments are Base64-encoded, which makes them about a third larger. Gmail Takeout exports often reach tens of gigabytes; the viewer reads them in pieces.
Is it safe to view an MBOX file online?
Only if the file isn't uploaded, since it contains your whole mailbox. The viewer on this page reads it locally in your browser and blocks remote images in emails, so nothing leaves your device.
Last updated .