Read any MBOX file on macOS
Macs come with Apple Mail, but Mail has no way to simply open an MBOX file and look inside. You can import it, which copies every message into Mail's library, or you can download a third-party app. For a Gmail Takeout export of several gigabytes, an import can take a long time and leaves you with a huge Import mailbox to clean up afterwards.
This page opens MBOX files in your Mac's browser. Drag the file from Finder and start reading. Nothing is copied into Mail, nothing is installed, and the file never leaves your Mac.
Mac-specific tips
Apple Mail exports are packages. When you use Mailbox → Export Mailbox in Apple Mail, you get an item like Clients.mbox. It looks like a file but is actually a folder. Chrome and Edge accept the whole package when you drag it onto the page. If your browser doesn't, Control-click the package, choose Show Package Contents, and drag the file named mbox instead. You can ignore Info.plist.
Takeout downloads unzip automatically in Safari. If Safari's "Open safe files after downloading" setting is on, your Takeout .zip may already have been extracted into a Takeout folder in Downloads. The MBOX is in Takeout/Mail/. Either the zip or the extracted .mbox works. More on that in the Google Takeout MBOX guide.
Mail's own library uses EMLX, not MBOX. If you're digging through ~/Library/Mail from a backup, the individual messages are .emlx files. Open them with the EMLX viewer.
Use Quick Look to check what you have. Select the file in Finder and press Space. A plain MBOX file shows as text starting with a From line. A package shows as a folder icon.
Opening MBOX on a Mac: the options
| Method | Good for | Drawbacks |
|---|---|---|
| InboxVue in Safari or Chrome | Reading, searching, exporting a few or many messages | Messages stay in the file rather than in Mail |
| Apple Mail: File → Import Mailboxes → Files in mbox format | Keeping messages in Mail for good | Slow for big files; Gmail labels are lost; adds an Import mailbox |
| Thunderbird for Mac + ImportExportTools NG | Keeping messages in Thunderbird | Install and add-on setup |
| Paid Mac viewer apps | Offline desktop use | Purchase and install |
Step-by-step instructions for each are in how to open an MBOX file.
Troubleshooting on macOS
"No valid mbox files were found" in Apple Mail. If you exported the mailbox from Apple Mail, choose Apple Mail rather than Files in mbox format in the import dialog, and import the whole .mbox package rather than the file inside. Unzip .mbox.gz files first. InboxVue opens all of these directly.
The browser seems slow on a very large file. Close other heavy tabs. On Macs with 8 GB of memory, files above roughly 10 GB index more slowly, but reading individual messages stays quick.
Downloads go to the wrong place. Bulk exports in Chrome let you pick a folder. In Safari they're saved to your Downloads folder, so check there.
Need documents rather than a viewer?
Export messages as PDFs with MBOX to PDF, or go back to the general MBOX viewer page for details on labels, threads and search.