How to Import Mailboxes into Apple Mail from Another App

Knowing how to import mailboxes into Apple Mail is the first step when you are switching from Thunderbird, Outlook, or an older Mac, or when you want to bring an archived mbox file into your current email client. The command is at File > Import Mailboxes in the macOS menu bar, and it handles several source formats natively — mbox folders, Outlook for Mac exports, and Eudora archives among them. What the import dialog does not explain is where the mail goes afterward and what you need to do to make it accessible on other devices.

The short answer: imported mail always lands in a local On My Mac folder called Import, not inside your iCloud account or any IMAP mailbox. That folder exists only on the Mac where you ran the import. Apple Mail does not upload it to iCloud automatically, and the messages will not appear on your iPhone or another Mac until you drag them into a server-side mailbox. Most support threads about missing imported mail come back to this single point.

This guide covers the full import process for macOS Ventura, Sonoma, and Sequoia — including which formats each source app produces, why the Import Mailboxes option sometimes appears greyed out or missing entirely, and how to move imported mail into the cloud once it arrives. The last section addresses what to do when Apple Mail on iPhone or iPad is involved: that platform has no import command, and the path there is different.

Before you start: formats, account types, and what to expect#

Apple Mail's import command accepts three broad source types: mbox folders, Microsoft Outlook for Mac data files with the .olm extension, and legacy archives from Netscape Communicator and Eudora. The most portable of these is mbox — it is the format Apple Mail produces when you use Mailbox > Export Mailbox, and it is what Thunderbird exports via the ImportExportTools NG add-on. Most modern mail clients can export as mbox even if they do not describe it by that name.

If your source is Outlook on Windows, the export format is a .pst file — a proprietary Microsoft format Apple Mail cannot open directly. You need a conversion tool such as Aid4Mail, libpst on the command line, or Thunderbird's own import function to extract the mail as mbox before Apple Mail can read it. Outlook for Mac exports a cleaner .olm format that Apple Mail handles natively, so if you have access to both Windows and Mac versions of Outlook, use Outlook for Mac to perform the export.

The mbox source file or folder must be on a local drive before you start. Apple Mail cannot read from a network share, an unmounted external volume, or a compressed archive during import. If your backup lives on an external drive, confirm it is connected and mounted. If it is inside a zip or tar archive, extract it to a local folder first.

One constraint that catches many users off guard: Apple Mail on iPhone and iPad has no File > Import Mailboxes command or any equivalent. If your archived mail needs to be accessible on iOS, import it on the Mac and then move the messages into an iCloud or IMAP mailbox so they sync to your other devices.

How to import mailboxes into Apple Mail, step by step#

These steps apply to macOS Ventura, Sonoma, and Sequoia. The menu path is the same across all three versions.

1. 1

   Export from your source application first

   From Thunderbird, install the ImportExportTools NG add-on and use it to export each mailbox as an mbox folder. From Outlook for Mac, go to File > Export and save as an Outlook for Mac Data File (.olm). From a previous Mac running Apple Mail, open that machine and use Mailbox > Export Mailbox to create a .mbox bundle, then transfer it to the current Mac. From Gmail or another web service, tools like Google Takeout can produce mbox exports. Place the exported file or folder on your Desktop or in your Documents folder so it is easy to navigate to during the import.

2. 2

   Open Apple Mail on the destination Mac

   The import runs on the Mac where you want the mail to appear. If you are moving from a Windows machine, transfer the exported file to the Mac first. Apple Mail does not require any particular account to be active for the import to work — imported mail goes into On My Mac regardless of which accounts are configured.

3. 3

   Choose File > Import Mailboxes from the macOS menu bar

   Click File in the menu bar at the very top of the screen — not a button inside the Mail window — then choose Import Mailboxes. If the option is greyed out, see the troubleshooting section below. A dialog opens asking you to choose a source type.

4. 4

   Select the format that matches your export

   Choose Files in mbox format for a .mbox folder from Thunderbird or Apple Mail. Choose Outlook for Mac for a .olm file. Choose Netscape or Eudora for archives from those clients. If none of these match, choose Other and navigate to the mbox file manually. After selecting the type, click Continue and navigate to the file or folder in the Finder sheet that appears.

5. 5

   Select which mailboxes to import and click Continue

   Apple Mail reads the archive structure and presents a list of the mailboxes it found. Each has a checkbox — deselect any folders you do not need to keep the import focused. When your selection is ready, click Continue. Mail begins importing in the background and shows a progress indicator in the status bar at the bottom of the Mail window.

6. 6

   Find the imported mail under On My Mac in the sidebar

   When the import finishes, expand the On My Mac section in the Mail sidebar and look for a folder called Import. Inside it are subfolders matching the names of your original mailboxes. Open a few messages to confirm they arrived correctly. From here, drag messages into an iCloud, Gmail, or other server-side mailbox to upload them to the cloud, or leave them in On My Mac if local access on this Mac is sufficient.

Import speed scales with archive size and your drive's read speed. A few hundred plain-text messages typically finishes in under a minute. A large multi-year archive with embedded attachments can take ten minutes or longer. Mail imports progressively, so the folder appears in the sidebar before all messages have finished loading — the count may rise as the background import continues. Wait for the status bar activity to stop and the count to stabilize before treating the import as complete.

Where imported mail lands, by source app#

Apple Mail handles each source format slightly differently at import time. The table below maps the most common sources to the export format you need, whether Mail reads it without conversion, and where the result ends up.

What to do when Import Mailboxes is greyed out or the mailbox does not appear#

The import command fails, or appears to succeed but leaves no visible result, in a small number of predictable ways. Each cause has a specific fix.

• Import Mailboxes is greyed out in the File menu: The source file or folder must be on a local, mounted drive. A greyed-out option almost always means the source is on a network volume, inside a zip archive, or on an external drive that has not fully mounted. Copy the mbox folder or .olm file to a folder on your internal drive first, then try the import again.
• Import Mailboxes does not appear in the File menu at all: Click the Mail window to bring it to the foreground, then check the File menu again. On macOS Ventura and later, the option may not be visible if no mail accounts are configured — add at least one account in System Settings > Internet Accounts, open Mail, let it sync, then return to File > Import Mailboxes.
• The import finishes but no Import folder appears in the sidebar: Look for the On My Mac section in the sidebar and expand it using the disclosure triangle. If On My Mac is not visible at all, go to Mail > Settings > General and enable Show On My Mac. Quit and reopen Mail if the section does not appear after toggling the setting.
• The imported mailbox is empty after import completes: The mbox archive may have contained a nested folder structure that Mail read without finding messages inside each file. Try importing an individual .mbox file by choosing Other in the source dialog and selecting the file directly. You can verify the file is valid by opening it in a plain text editor — a well-formed mbox file begins with the word From followed by a sender address on the very first line.
• Apple Mail Import Mailboxes option is greyed out after a macOS update: A permissions reset during the upgrade can block Mail from reading the local disk. Open System Settings > Privacy and Security > Full Disk Access and confirm Apple Mail is listed and enabled. If it is not listed, click the plus button, navigate to Mail in the Applications folder, and add it.
• Imported messages show blank senders or missing message bodies: This most often happens with .pst archives converted by a third-party tool that did not handle the message header encoding correctly. Try a different conversion utility, or export from Outlook for Mac as .olm and import that file directly into Apple Mail rather than going through .pst.

The distinction between importing and migrating is worth keeping clear. Apple Mail's import command is a one-time archival operation — it reads a static export file and copies the messages into On My Mac. It does not stay connected to the source application, does not pull new messages from Thunderbird or Outlook on an ongoing basis, and does not replace adding an IMAP account if you want live mail access going forward. If you are switching your primary client rather than archiving old mail, the right path is to add your accounts directly in Mail settings and let them sync via IMAP or Exchange.

Moving a large imported archive from On My Mac into iCloud or Gmail is best done in batches. Selecting several thousand messages and dragging them all at once can cause the upload to stall or time out. Move in groups of two hundred to five hundred messages, wait for each batch to finish uploading — the account's folder count stabilizes and the activity indicator in the status bar goes quiet — then move the next group.

A faster way to unify accounts without importing archives#

The import path solves a specific problem: you have a static archive of old mail in a file that needs to land in Apple Mail. If the broader goal is consolidating mail from several active accounts into one view, getting AI-assisted triage without manual sorting, or switching away from Apple Mail because it is not keeping up with a multi-account workload — importing mbox files is not the most direct answer to any of those.

We build AI Emaily, an AI-native email client that connects Gmail, Outlook, iCloud, and any IMAP account in a single unified inbox without requiring exports or imports. Your mail stays on each provider's server; AI Emaily shows everything together, handles triage through autonomy levels you control, and drafts replies in a voice defined by a Context Brain you configure — not by training on your past mail. If you are migrating away from Apple Mail because managing multiple accounts there has become unwieldy, AI Emaily's 7-day free trial at aiemaily.com/pricing lets you evaluate whether a different architecture suits your workflow.