How to open an MBOX file on Windows and Mac

What an MBOX file is

MBOX is one of the oldest email storage formats. A single MBOX file holds a whole mailbox: every message is stored one after another as plain text, each starting with a line that begins with From . Attachments are stored inside the messages, encoded as text.

Because it is a simple, open format, many apps can export and import it. Google Takeout gives you Gmail as one big MBOX, Thunderbird keeps every folder as an MBOX file, and Apple Mail exports mailboxes in it. For how it differs from Outlook’s format, see MBOX vs PST.

Before you start: copy and unpack

1. Make a copy of the file and work on the copy. Some tools rewrite or move what they import, and a stray save in a text editor can damage the original.
2. Extract archives first. Google Takeout delivers a .zip or .tgz file. Unpack it (double-click on a Mac, right-click → Extract All on Windows) and look for a file such as All mail Including Spam and Trash.mbox inside the Takeout/Mail folder. Our Google Takeout guide walks through the export.
3. Check the size. A Takeout MBOX can easily be several gigabytes. That affects which method is practical.

Option 1: Thunderbird (free, Windows, Mac and Linux)

Mozilla Thunderbird is a free email app, and with the free ImportExportTools NG add-on it is the most versatile way to open an MBOX file. You don’t need to set up an email account to use it.

1. Install Thunderbird from thunderbird.net. If it asks to set up an account, you can skip or cancel that.
2. Open Add-ons and Themes from the ☰ menu, search for ImportExportTools NG and add it.
3. In the folder pane, right-click Local Folders and choose ImportExportTools NG → Import mbox file.
4. In the dialog, choose to import one or more individual MBOX files (or, if you have a folder of them, the option that includes subfolders), then select your file.
5. Wait for the import to finish. The mailbox appears as a folder under Local Folders, where you can read, search, sort and open attachments as usual.

Large files take a while, so let Thunderbird work until the message count stops changing. Keep in mind that Thunderbird copies the mail into its own profile folder, so a 5 GB MBOX uses another 5 GB of disk space.

Option 2: Apple Mail on a Mac

If you are on a Mac, the built-in Mail app can import MBOX files without any add-on.

1. Open Mail and choose File → Import Mailboxes…
2. Select Files in mbox format and click Continue.
3. Select the folder that contains the MBOX file (not the file itself), then continue. For an Apple Mail export, choose the .mbox folder.
4. When it finishes, look in the sidebar for a new mailbox called Import, usually under On My Mac.

You can drag messages or folders from Import into other mailboxes and delete it afterwards. As with Thunderbird, Mail stores its own copy of everything you import.

Option 3: A text editor, for a quick look

Since MBOX is plain text, any text editor can show what’s inside. That’s handy for checking which account a file came from or finding one message by searching for a word. It is not a comfortable way to read mail, though:

• Large files can freeze Notepad or TextEdit. For anything over a few hundred megabytes, use an editor built for big files (many programmers’ editors handle them well).
• Attachments and images appear as long blocks of seemingly random letters (base64), and HTML emails show their raw code.
• Accented characters may show up encoded, for example as =C3=A9.

Option 4: Convert to PST to open it in Outlook

Outlook can’t open or import MBOX files, on Windows or Mac. If Outlook is where you want to work with the mail, the file needs converting to a PST (Outlook Data File) first. Our comparison How to convert MBOX to PST covers four ways to do it, including a free one through Thunderbird and an IMAP account.

MoveMyInbox is the online option: you upload your MBOX files from a browser on any computer, see a one-time price based on their size (see pricing), and download a single PST, usually within minutes. Folders, Gmail labels, attachments and read/flagged status are kept. You then open the PST in Outlook as described in our PST import guide.

Other apps that read MBOX

On Linux, the Evolution mail client can import MBOX files through its import assistant, and terminal mail programs such as mutt can open an MBOX file directly (mutt -f filename). Some other desktop email clients offer MBOX import too; check their help pages.

You will also find dedicated “MBOX viewer” apps and websites. Be careful with both:

• Online viewers require uploading your mail. Years of personal email can contain bank details, medical letters and passwords, so read how the site stores and deletes uploads before using it, or avoid it.
• Downloaded viewer apps should come from the developer’s own site or an official app store. Avoid installers from unknown download portals.

Which option for which goal

Troubleshooting: empty or garbled mail

The import finished but the folder is empty

• Wrong file. You may have picked a Thunderbird .msf index file, or an Apple Mail metadata file instead of the file named mbox.
• It’s still an archive. A Takeout download renamed or only partly extracted is still a ZIP. Unpack it and import the file inside.
• It isn’t MBOX at all. A folder full of small files in cur, new and tmp subfolders is Maildir, a different format. The MBOX import steps above won’t read it; look for an app that imports Maildir.
• The file is incomplete. Open the copy in a text editor: the very first line should start with From . If it doesn’t, the export may have failed; try exporting again.

Strange characters in subjects or text

Garbled accents usually mean the app guessed the wrong character set. Try another option from this list (Thunderbird handles character sets well), or change the text encoding in the app’s view menu for that message. If only a text editor shows gibberish, that’s expected: it shows the encoded raw text.

Frequently asked questions