Open an .mbox mail archive, such as a Gmail export from Google Takeout or a Thunderbird or Apple Mail folder, and browse every message in your browser. Search senders, subjects or full text, filter by Gmail label, read messages safely, save attachments and export messages as .eml files.
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Select a message to read it.
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How to use the MBOX File Viewer
Open the archive: drop an .mbox file on the box or click to choose it. A small sample mailbox is shown until you do.
Find messages with the search box, the label filter and the sort menu. Tick Also search message text to search inside bodies.
Read a message by clicking it. Switch between HTML, plain text and the full headers.
Save attachments with the Download buttons under the message.
Export the message as .eml, all listed messages as a ZIP of .eml files, or the list as a CSV spreadsheet.
Where mbox files come from
Source
How to get the mbox file
Gmail (Google Takeout)
Request a Takeout export with Mail selected, download and unzip it, then open the .mbox file in the Takeout/Mail folder.
Thunderbird
Local folders are already mbox files without an extension, stored in the profile folder under Mail or ImapMail (for example Inbox, Sent). Copy one and open it.
Apple Mail
Select a mailbox, choose Mailbox › Export Mailbox. The export is a .mbox folder that contains a file named mbox.
Linux and server mail
Spool files such as /var/mail/username and folders kept by mutt, alpine or Evolution are usually mbox.
How an mbox file is structured
Each message begins with a separator line such as From [email protected] Mon Sep 08 09:14:02 2025, followed by the normal email headers (From, To, Subject, Date, Message-ID), an empty line and the body. The next separator starts the next message. Bodies are stored exactly as received, so HTML parts, attachments in base64 and quoted-printable text are all inside the file.
mboxo and mboxrd are the two common variants. Both escape body lines that start with From by adding >; mboxrd also escapes lines that already start with >From . The viewer reverses one level, which is correct for both in normal mail.
Line endings may be LF (Unix) or CRLF (Windows); both are handled.
Labels and folders: Gmail adds an X-Gmail-Labels header listing every label of the message, which powers the label filter here.
Tips
Type several words to narrow the list: every word must match, so invoice march finds messages that mention both.
Sort by size to find the messages with the biggest attachments.
Export the list as CSV to get a spreadsheet of dates, senders and subjects for record keeping.
For a single message saved as .eml, the EML File Viewer shows every MIME part; to check where a message came from, paste its headers into the Email Header Analyzer.
Frequently asked questions
What is an MBOX file?
MBOX is a long-standing format for storing a whole mail folder in one plain-text file. Messages are written one after another, and each starts with a separator line beginning with "From " followed by the sender and date. Gmail's Google Takeout export, Thunderbird's local folders, Apple Mail exports and many Linux mail programs use it.
How do I open my Gmail Takeout mbox?
Download your Takeout archive, unzip it, and open the file named like All mail Including Spam and Trash.mbox from the Mail folder. Gmail labels are read from the X-Gmail-Labels header, so you can filter by Inbox, Sent or any label you created.
Is there a size limit?
Files up to 1 GB can be opened, depending on your device's memory. Only the headers are indexed when the file opens; each message is decoded when you click it. Full-text search indexes bodies on first use, which can take a little while for very large archives.
Are my emails uploaded?
No. The file is read and decoded by JavaScript on your device and is never sent to a server. The only optional network requests are remote images in an HTML email (blocked until you allow them) and the ZIP library when you export several files at once.
What is the difference between MBOX and EML?
An .eml file holds a single message, while an .mbox file holds many messages in sequence. Exporting a message as .eml lets you open it in Outlook, Apple Mail or Thunderbird, attach it to another email, or keep it as a separate record.
Why do some lines start with >From?
Inside an mbox, a body line that begins with "From " would look like the start of a new message, so mail programs add a > in front of it. The viewer removes one level of this escaping when it shows or exports a message.
Can it open Outlook PST files?
No. PST and OST are Microsoft's proprietary binary formats. Use Outlook or another mail program to export the folder as mbox or as .eml files, or use an mbox from a different source.
Are all the tools on FreeToolCabin tested for quality and accuracy?
Yes! Every tool on our site undergoes automated Q/A testing in real browser environments to ensure high precision, correct output, and zero errors. If you happen to spot a bug or have a suggestion, please contact us at [email protected] and our team will review it right away.