How to Open an Apple Mail Export (.mbox Folder) on Mac

Apple Mail (the built-in Mail app on macOS) can export any mailbox to the open mbox format. It’s the perfect way to archive old mail, hand a mailbox to someone else, or keep a copy outside of Mail. The export has one quirk worth knowing about — let’s walk through it.

Step 1: export the mailbox from Apple Mail

1. Open Mail and select the mailbox you want to export in the sidebar.
2. Choose Mailbox → Export Mailbox… from the menu bar.
3. Pick a destination folder and click Choose.

Mail writes the export to the folder you picked.

Step 2: understand what Mail actually exported

Here’s the quirk: Apple Mail doesn’t export a single file. It creates a folder named after your mailbox, ending in .mbox — for example Inbox.mbox or Receipts 2019.mbox. Inside that folder you’ll find:

• a file named simply mbox — this is the real archive, with every message in standard mbox format
• one or more .plist files — metadata that Mail uses internally; you can ignore them

So Inbox.mbox is a container; the file called mbox inside it is your mail.

Step 3: open the inner “mbox” file with Mbox Viewer

1. In Finder, open the exported folder (e.g. Inbox.mbox).
2. Take the file named mbox inside it.
3. Drag it onto Mbox Viewer (or use File → Open in Mbox Viewer and select it).

That’s it. The file opens read-only, your original export is never modified, and you can search, browse threads, preview attachments and export individual messages to EML, CSV or text.

Nested mailboxes

If you export a mailbox that contains sub-mailboxes, Mail creates nested .mbox folders. Each level has its own inner mbox file — open each one the same way.

Why this beats re-importing into Mail

Re-importing an archive into Apple Mail mixes it back into your live mail and can take a long time for big exports. Opening the export with Mbox Viewer keeps the archive exactly as it is — a self-contained, read-only snapshot you can search instantly, even when it’s tens of gigabytes.