MBOX file viewer

How to open an .mbox file

1. Choose the .mbox file, or drop it on the page. Large mailboxes are read a piece at a time, so a multi-gigabyte export works; a bar shows the progress.
2. Find messages. Every message is listed, newest first. Search by sender, recipient or subject, or pick a Gmail label.
3. Read one by clicking its subject. Only that message is read from the file, so it opens quickly.
4. Save what you need: the message as a PDF or .eml, its attachments, one PDF of the messages listed, or a spreadsheet of them.

What is an .mbox file?

An .mbox file holds a whole mail folder: every message, one after another, in the internet’s standard message format, each starting with a line that begins with “From ”. It is the format of Google Takeout’s Gmail export and of Thunderbird’s folders, and Apple Mail exports mailboxes in it. Because it is plain text, it is a good long-term archive, but most mail programs can only import it, not browse it.

Where .mbox files come from

• Gmail: Google Takeout exports Mail as .mbox files inside its .zip archives. Takeout splits the archive, not the mailbox, so the .mbox inside can be far bigger than the archive size you chose; the viewer reads it a piece at a time. Labels are kept in each message, so you can filter by them here.
• Thunderbird: each local folder is an mbox file without an extension, such as Inbox, in the profile’s Mail folder. Choose that file here.
• Apple Mail: Mailbox → Export Mailbox makes a folder ending in .mbox. The file to choose is the one named mbox inside it.

To put a mailbox back into a mail program, Thunderbird (with the ImportExportTools NG add-on) and Apple Mail (File → Import Mailboxes) import .mbox files; Outlook doesn’t. To move single messages into Outlook, save them here as .eml files.

Saving as PDF

There are two ways, both on your device:

• Download PDF makes the PDF straight away: the subject, sender, recipients and date at the top, then the message text and the list of attachments. Long messages run over as many pages as they need. This PDF uses standard fonts, which cover English and Western European languages; other letters (Polish, Czech or Greek ones, Chinese, Arabic) and emoji print as “?”, and you are told when that happens.
• Print or save as PDF opens your browser’s print window with the message as it looks on screen, pictures included. Choose Save as PDF (or Microsoft Print to PDF on Windows) as the printer. This keeps the layout and every alphabet.

With several messages, One PDF of the messages listed puts them all in one file, each starting on a new page. Search first to include only some of them.

Private by design

Nothing is uploaded. The files are read by your browser on your device, and pictures from the web inside a message are not loaded, so the sender can’t tell the message was opened.

Outlook, Exchange and Microsoft 365 are trademarks of Microsoft; Gmail and Google Takeout of Google; Apple Mail of Apple; Thunderbird of the Mozilla Foundation. SheetConvert isn’t affiliated with any of them; the names are used only to say which files the tools open.