How to open MBOX files on a Mac without importing

Apple Mail can import MBOX, but you do not have to. This is how to read the files directly on macOS, including .mbox packages.

Updated 3 min readmacOS
Silver laptop showing a Mac-style Finder window with MBOX files in the Downloads folder

On a Mac, the obvious route is to import an MBOX file into Apple Mail. That works, but it adds hundreds or thousands of old emails to your mail database, where they mix with current mail and get indexed by Spotlight. If you only need to read or search the archive, keeping it in a separate program is cleaner.

Understand the .mbox package before using MBox Viewer alternatives

When Apple Mail exports a mailbox, the result looks like a single file named, for example, Clients.mbox. It is actually a folder that macOS displays as one item.

To see inside, Control-click it and choose Show Package Contents. You will usually find:

  • mbox – the file that holds the messages. This is what you open.
  • table_of_contents or Info.plist – index data used by Mail. You can ignore it.

Files from Google Takeout, Thunderbird or a server are ordinary single files and need no unpacking.

Read it in Thunderbird when MBox Viewer is not available

Thunderbird for Mac is free and keeps the archive in its own program, away from your Apple Mail mailboxes.

  1. Install Thunderbird. When it asks you to set up an email account, you can close that window.
  2. Open the menu, choose Add-ons and Themes and install ImportExportTools NG.
  3. Right-click Local Folders and choose ImportExportTools NG → Import mbox file.
  4. Select the file. For an Apple Mail package, choose the inner mbox file. Press Command-Shift-G in the dialog to type a path.
  5. A new folder appears under Local Folders. Click it to read the messages.

Tip: if the file dialog will not enter the package, copy the inner mbox file to your Desktop first and import that copy. MBox Viewer, offered in our download section, is a Windows program; if you also have a Windows PC, copying the file there is another quick route.

If you want it in Apple Mail instead of MBox Viewer

For long-term use, importing can make sense:

  1. Open Mail and choose File → Import Mailboxes.
  2. Select Files in mbox format and click Continue.
  3. Pick the file or folder and confirm.

The messages appear under a new Import mailbox in the sidebar, stored on your Mac rather than in any online account. You can move them or delete the whole folder later.

Mac permission prompts when opening MBOX files and MBox Viewer alternatives

Recent versions of macOS protect folders such as Desktop, Documents and Downloads. If Mail or Thunderbird asks for permission to access a folder when you pick a file, allow it. The access is used only to read the file you selected.

Very large archives on a Mac without MBox Viewer

Importing copies every message, so you need free disk space at least as large as the archive. Multi-gigabyte imports can take a long time. If one stalls, split the file into smaller parts using the method in our article on large MBOX files and import the parts one by one.

Quick MBox Viewer checklist for opening MBOX files on Mac

  • Back up the original .mbox file or package first.
  • Use the inner mbox file for Apple Mail exports.
  • Copy the inner file out of the package if the file dialog will not enter it.
  • Check free disk space before importing a large archive.

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