MBOX Viewer by Read Mbox
mbox on windows · nothing is uploaded

How to open an MBOX file on Windows

Windows has no built-in app for .mbox files, and Outlook can't import them. Open Edge (already on every Windows PC) or Chrome and open the file at readmbox.com. Nothing is installed and nothing is uploaded.

Open your .mbox file
Free to read · runs in your browser · nothing is uploaded

Why Windows can't open it

Double-click an .mbox file and Windows asks which app to use, because nothing on a normal Windows PC reads the format. Outlook only imports PST and CSV. The Mail app and the new Outlook don't import MBOX either. Notepad shows raw text and freezes on big files.

Option 1: in the browser (no install)

  1. Unzip your export. In File Explorer, right-click the Takeout .zip and choose Extract All. The mail is in Takeout\Mail\.
  2. Open Edge or Chrome and go to readmbox.com.
  3. Drag the .mbox file in. It's read in place, so even a 30 GB file won't need a copy or an upload.

This works on locked-down work PCs too, where you can't install software.

Option 2: Thunderbird

Thunderbird is a free email program that reads MBOX. Install it, skip the account setup, then copy the .mbox into its Local Folders directory while Thunderbird is closed. On Windows that folder is usually:

%APPDATA%\Thunderbird\Profiles\<profile>\Mail\Local Folders\

Paste %APPDATA%\Thunderbird\Profiles into the File Explorer address bar to get there. Restart Thunderbird and the file appears under Local Folders. If it doesn't show up, see the fixes.

Be careful with "free MBOX viewer" downloads

Many Windows MBOX tools are installers from companies you've never heard of. Some are only demos that block exporting until you buy a Pro version, and unsigned installers often trigger Windows SmartScreen warnings. If you do install one, download it from the publisher's own site.

Need it in Outlook?

Export the messages as .eml files here and drag them into an Outlook folder. Step-by-step guide.

Video: three ways to open an MBOX file

How to Open & Read MBOX Files – 3 Easy Ways (ReadMbox, Thunderbird, Apple Mail) on YouTube

Common questions

How do I open an MBOX file on Windows 10 or 11?

Open it in Edge or Chrome at readmbox.com. Nothing is installed or uploaded. Or install Thunderbird and copy the file into its Local Folders directory.

Can Windows Mail or Outlook open MBOX?

No. Neither imports MBOX. Convert the messages to EML and drag them into Outlook if you need them there.

Where does Thunderbird store mail on Windows?

In %APPDATA%\Thunderbird\Profiles\<profile>\Mail\Local Folders\ for local mail. Each mailbox is a file with no extension, next to an .msf index file.

Do I need admin rights?

Not for the browser viewer. It runs in Edge or Chrome like any website, so it works on PCs where you can't install software.

Outlook can't open MBOX

Why Outlook can't do it, and the two ways around it: read it in a browser, or move it in as EML.

Open an MBOX file on Mac

Apple Mail exports are folders, where Mac mail apps keep their mailboxes, and how to read them.

Thunderbird MBOX import not working

File not showing up, wrong folder, frozen on a big Takeout file: the fixes.

Open a large MBOX file (10 GB+)

Why big Takeout files crash other apps, and how to open one without importing anything.

Ready? Your file stays on your computer.

Open your .mbox file