# Where to Find Your mbox Files on Windows, Mac and Linux ## What an mbox file actually is An mbox file is one large text file in which a mail program stores an entire folder of messages back to back. A single file can hold thousands of emails, attachments included. Clients like Thunderbird, Apple Mail and older Unix mailers have used this format for decades. Alongside mbox you will run into related variants: .mbx, individual .eml and .emlx messages, Outlook's .msg, Maildir folders (where each email is its own small file) and .mbox.gz from Google Takeout. The catch is that mail clients like to tuck these archives away in folders you normally never see. In this article we show, per operating system, where they live, how to reveal hidden folders, and how to open the file safely and locally afterwards. :::info title="Everything stays on your own device" Mbox Viewer is a Chrome extension that processes your email 100% locally. Nothing goes to a server or the cloud, there is no telemetry, and the Chrome permissions are empty. You drag a file into the window and it is read inside your own browser (IndexedDB). Learn more at https://mbox-viewer.online ::: ## Why you want to find these folders Maybe you are switching to a new mail client, searching an old archive, running a legal or forensic investigation, or simply want to read emails without downloading them again. In every one of those cases you need the raw mbox file. Once you know where it lives, you can open, search, tag and export it with Mbox Viewer without reconnecting your old account. ## Show hidden folders first Many mail folders sit inside hidden system folders. Reveal those first, otherwise they will not appear in your file browser. :::howto title="Show hidden folders per system" 1. Windows: open File Explorer, click View at the top, choose Show, and tick Hidden items. 2. macOS: open Finder and press Command + Shift + period to reveal hidden files. Press again to hide them. 3. macOS Library: in Finder hold the Option key, click the Go menu, and choose Library. 4. Linux: in your file manager (such as Files or Nautilus) press Ctrl + H to show hidden folders that start with a dot. ::: ## Where it lives on Windows On Windows, Thunderbird is by far the most common source of mbox files. The messages sit in your profile folder. - Open the folder: press the Windows key + R, type %APPDATA%\\Thunderbird\\Profiles and press Enter. - Open the profile folder (often something like randomletters.default-release). - Local folders and POP accounts live in the Mail subfolder, IMAP accounts in ImapMail. - Each folder has two files with the same name: the file with no extension (for example Inbox) is the mbox archive, while the file ending in .msf is only an index. If you have a backup from Outlook or another client, you usually export to .eml, .msg or .mbox first before opening it. A .mbox.gz from Google Takeout does not need unpacking: Mbox Viewer does that automatically. :::tip title="You do not need the .msf file" The file without an extension holds the real email content. The matching .msf file is just a quick index for Thunderbird itself. So drag the file without an extension into Mbox Viewer. ::: ## Where it lives on macOS On a Mac you typically face two situations: Apple Mail and Thunderbird. - Apple Mail stores messages in ~/Library/Mail. There you will find per-account subfolders with .emlx files and .mbox structures. The Library folder is hidden by default, so reveal it first (see the steps above). - For a clean mbox out of Apple Mail, select the folders in Mail, choose Mailbox, then Export Mailbox. You get a .mbox package you can drag into Mbox Viewer. - Thunderbird on the Mac keeps its profile in ~/Library/Thunderbird/Profiles, with the same Mail and ImapMail structure as on Windows. :::warn title="Copy first, never work inside the original folder" Never work directly in the active mail folder while your mail client is open. Quit the program or copy the file to, say, your desktop first. That prevents a running client from corrupting the archive while you open it. ::: ## Where it lives on Linux On Linux it depends on your client. - Thunderbird keeps its profile in a hidden folder: ~/.thunderbird (on some systems ~/.mozilla-thunderbird). Inside it you again find Mail and ImapMail folders with the extensionless mbox files. - Classic Unix mailers often use one system mbox per user in /var/mail or /var/spool/mail. - Many modern clients (such as KMail or a local mail server) use Maildir instead of mbox. With Maildir each email is a separate small file in subfolders named cur, new and tmp. Mbox Viewer can read an entire Maildir folder, so just drag the parent folder into the window. ## Opening the file with Mbox Viewer Once you have found the file, opening it is very quick. :::howto title="Open an mbox file" 1. Open Chrome and launch the Mbox Viewer extension. 2. Drag your .mbox, .mbx, .eml, .emlx, .msg, .mbox.gz or your whole Maildir folder into the window (drag and drop). 3. Wait for the messages to load. A .mbox.gz is unpacked automatically. 4. Read the message list on the left and the message on the right, just like Gmail or Thunderbird. 5. For each message, click the Preview, Raw or Forensic tabs for more detail. ::: Notice that images in an email do not load? That is on purpose. External images are blocked by default so senders cannot follow you through an invisible tracking pixel. If you do want to see them, click the per-message button to load images. :::tip title="Search with operators" Mbox Viewer has a powerful search bar. Try from:name, has:attachment, after:2024-01-01, larger:5M or "exact phrase" between straight quotes. You can save searches and even switch to a regex mode. ::: ## Prefer to export a clean copy instead Rather than hunting down the raw profile file, you can often export cleanly from your mail client. In Thunderbird, the ImportExportTools NG add-on writes a folder out as mbox; in Apple Mail you pick Mailbox, then Export Mailbox. Both produce a file you drag straight into Mbox Viewer. From there, Mbox Viewer can export again to PDF, .eml, .html or back to .mbox, in bulk too. :::faq ### What is the difference between mbox, eml and Maildir? An mbox is one large file holding all of a folder's messages back to back. An .eml is exactly one single email message. Maildir is a folder structure where each email is its own small file inside subfolders named cur, new and tmp. Mbox Viewer opens all three kinds. ### I cannot see the mail folder in my file browser. What now? The folder is probably inside a hidden system folder. Turn on hidden items first: on Windows via View and Show, on macOS with Command + Shift + period, and on Linux with Ctrl + H. After that, folders like .thunderbird and the Library folder appear on their own. ### Are my emails uploaded when I open them? No. Mbox Viewer works fully locally and offline. Nothing goes to a server, there is no telemetry, and the extension has empty permissions. All data stays inside your own browser and you can wipe it any time through Settings and Clear database. ### Do I need to unpack a .mbox.gz from Google Takeout first? No, you do not. Just drag the .mbox.gz file into the window; Mbox Viewer unpacks it for you automatically and loads the messages. ### Can I open an entire Maildir folder at once? Yes. Drag the parent Maildir folder (the one containing the cur, new and tmp subfolders) into the window. Mbox Viewer then reads every individual message in that folder. ### Where do I get the extension and read more? Visit the homepage https://mbox-viewer.online for installation and guidance. The extension is built by Cloud Captains, see https://cloud-captains.com :::