A fast, private MBOX file viewer
An MBOX file is an entire mailbox in one file. You probably have one because you exported your Gmail with Google Takeout, backed up a Thunderbird folder, exported a mailbox from Apple Mail, or inherited an archive from an old server. These files are often huge, from hundreds of megabytes to tens of gigabytes, and the usual way to read them is to import them into a mail client, which takes time and fills your mail app with old messages.
InboxVue opens the MBOX in a browser tab instead and shows it as a familiar three-pane inbox. Nothing is imported or uploaded, and nothing changes on disk.
Made for big mailboxes
The viewer scans the file in 8 MB slices on a background thread, recording where each message starts. The list fills as it goes, and the first 200 messages normally appear in under three seconds, even for a 5 GB Takeout file. Opening a message reads just that part of the file, so it's instant however large the mailbox is. Search starts with senders and subjects and adds message text as indexing finishes; for very large archives the index is kept in your browser's private storage so it isn't rebuilt every time.
Google Takeout often splits a large export into several .zip parts. Drop all the parts at once, or drop the .zip without extracting it, and InboxVue finds the MBOX inside.
Gmail labels, threads and attachments
- Labels become folders. Takeout records every label in each message's
X-Gmail-Labelsheader. You'll see Inbox, Sent, Starred, Important, the category tabs and your own labels with their nesting. - Conversations stay together. Messages are linked by Gmail's thread ID or by the standard References header, so a reply chain reads in order.
- Attachments are one click away. Use the "Has attachments" view to find them, preview images and PDFs, and download single files for free.
Troubleshooting
The file has no extension. Thunderbird stores each folder as an MBOX file with no extension, such as Inbox or Sent, next to a .msf index file. Drop the extensionless file; ignore the .msf. Details are in the Thunderbird MBOX guide.
"The mailbox ends unexpectedly." The last message is incomplete, which usually means the download or copy was cut short. All the complete messages before it are still readable.
My Apple Mail export is a folder called Something.mbox. On a Mac this is a package. Drop the whole package, or open it with Show Package Contents and drop the file named mbox. The MBOX viewer for Mac page covers this in detail.
Some messages show odd characters. Old archives can mix character sets. Change it per message with ⋯ → Text encoding.
MBOX viewer vs importing into a mail client
| InboxVue | Thunderbird with ImportExportTools NG | Apple Mail import | |
|---|---|---|---|
| Install needed | No | Thunderbird plus an add-on | Mac only |
| Time before you can read | Seconds | Import time grows with file size | Import time grows with file size |
| Changes your mail setup | No | Adds local folders | Adds an Import mailbox |
| Gmail labels | Shown as folders | Not preserved | Not preserved |
| Export to PDF/CSV | Yes | Through the add-on's tools | Print one at a time |
If you want the messages permanently in a mail app, importing is the right choice. Our guide on how to open an MBOX file explains every method. To read a Google Takeout MBOX, search it or pull a few messages out, the viewer is quicker. When you need documents, export to MBOX to PDF or build a spreadsheet with MBOX to CSV.