What an MBOX file is
MBOX is the oldest way to store email: all messages of a folder in one plain file, one after another, each starting with a line that begins with “From ” (RFC 4155). It is simple, so many programs use it.
Open an MBOX file
Read a Gmail export from Google Takeout, a Thunderbird folder, an Apple Mail mailbox, or a single .eml message. Search by subject or sender, read messages, save attachments. The mailbox stays on your device.
Drop your .mbox or .eml file here
or
Your file stays on this device: it is read here, in your browser, and never uploaded.
Google Takeout, Thunderbird or Apple Mail mailboxes, or a single .eml message.
How it works
Choose the .mbox or .eml file
For Apple Mail exports, choose the file named “mbox” inside the exported .mbox folder.
We index it once
Your browser reads the file from start to end to find where each message begins. Large files take longer; you see the progress.
Search and read
Messages are listed newest first. Filter by Gmail label, search by subject or sender, open a message, save its attachments or the whole message as .eml.
MBOX files, explained
Where you get one
- Google Takeout. Exporting Gmail gives one file, usually called “All mail Including Spam and Trash.mbox”, often several gigabytes. Gmail labels are kept in each message (the X-Gmail-Labels header), and the viewer lets you filter by them.
- Thunderbird. Each folder is an MBOX file without an extension (Inbox, Sent…) in the profile’s Mail or ImapMail folder. The .msf files next to them are only indexes.
- Apple Mail. Mailbox → Export Mailbox creates a folder ending in .mbox; the messages are in the file called “mbox” inside it.
- Servers and old systems. Unix mail spools, cPanel and many backup tools use MBOX.
Why it won’t open
Windows has no program for MBOX, and Outlook cannot import it. Thunderbird and Apple Mail can import it, but that means setting up a mail program and copying gigabytes into it just to read a few messages. A text editor shows the raw messages, but attachments appear as long blocks of encoded text, and editors struggle with multi-gigabyte files.
What this viewer does
- Reads MBOX files of up to 32 GB and up to a million messages, without loading them into memory: only the position, subject, sender, date and labels of each message are kept.
- Lists messages newest first, searches subject and sender, filters by Gmail label.
- Shows a message with its text; HTML emails are shown in a locked-down frame, without remote images.
- Saves attachments, and saves any message as an .eml file that Outlook, Apple Mail and Thunderbird open.
- Also opens a single .eml message.
What it does not do
- It does not convert the mailbox to Outlook (.pst) or export many messages at once.
- Search covers subject and sender, not the message text.
- It does not change the file.
Frequently asked questions
How do I open my Google Takeout mbox file?
Unzip the Takeout download, then choose the .mbox file in the “Mail” folder here. Large exports take longer to index (you see the progress); then you can search and read them.
Is the mailbox uploaded?
No. It is read in your browser and never leaves your device. The page’s security rules stop it from sending data to other sites, and neither the file nor its name is sent to our own domain.
Can I search by Gmail label?
Yes. If the file comes from Google Takeout, a label menu appears with each label and its message count.
How do I open a Thunderbird mailbox?
In your Thunderbird profile, open the Mail (or ImapMail) folder and choose the file named after the folder, such as “Inbox”, the one without an extension. Not the .msf file.
Can I import the messages into Outlook?
Save the messages you need as .eml and drag them into an Outlook folder. Converting a whole mailbox to .pst is not available.
Can I open a single .eml file here?
Yes. Choose it like an mbox file: the message opens directly, with its attachments.