How to Transfer Apple Mail Emails to a Windows PC

When you switch from a Mac to a Windows PC, almost everything transfers without effort — files, photos, browser history. Email is the exception. Apple Mail stores its messages in its own format on disk, and that archive does not open on Windows without deliberate steps. The right steps depend on one key question: is your mail sitting on an IMAP server, or does it live entirely on the Mac as a local 'On My Mac' mailbox?

There are two honest routes. If your mail is in an IMAP account — Gmail, iCloud, Outlook.com, Fastmail, or any standard service — the simplest transfer requires no file conversion at all. Move the folders into your IMAP account on the Mac side, and the server replicates them to every connected client. Open the same account on Windows and the messages are already there. If you have local mailboxes that never touched a server, you need to export them as .mbox files, carry those files to Windows, and import them into Outlook or Thunderbird.

This guide covers both routes. Start with the IMAP method if it applies — it is the safer path, produces no orphaned files, and skips the conversion step entirely. The .mbox route is reliable when you genuinely need it, but it has more failure points and the right import tool depends on which client you land on.

Before you start#

Three checks before you touch anything prevent most of the common failures.

• Know where your mail actually lives. Open Apple Mail and expand the sidebar. You will see two categories: your IMAP account name — Gmail, iCloud, or similar — and 'On My Mac.' Messages under the account name are synced to a server and reachable on any device right now. Messages under 'On My Mac' exist only on this machine and need to be moved deliberately.
• Back up Apple Mail before moving anything. Apple Mail stores messages in ~/Library/Mail/. Open Finder, hold the Option key, click the Go menu, and select Library. Copy the entire Mail folder to an external drive or cloud storage. If something goes wrong during the transfer, this copy is your fallback.
• Set up your email account on the Windows machine first. Whether you are using Outlook, Thunderbird, or another client, the account needs to be connected and the initial sync complete on the Windows side before you start the transfer. Log in, let it finish, then come back to the Mac.

Method 1: Copy emails through your mail server (IMAP)#

IMAP keeps email synchronised between a server and every client that connects to it. RFC 3501 defines this as the core promise of the protocol: messages belong to the server, and every client that authenticates against that server sees the same state. When a message or folder lives under an IMAP account in Apple Mail, it already exists on the server — any other client that connects to the same account sees it immediately. No export, no file transfer between machines, no conversion. This is the method to use whenever you have the choice.

The steps below move messages from 'On My Mac' local folders into your IMAP account so the server propagates them to Windows. If you are moving from one IMAP account to another — say, from an old iCloud address to a Gmail account — add both accounts to Apple Mail and drag folders from one to the other. The destination account's server receives the messages as you drag.

1. 1

   Add your IMAP account to Apple Mail on the Mac

   Open Mail, go to Mail > Add Account, and sign in to the account you plan to use on Windows. Let the initial sync finish so the account folders are visible in the sidebar. Gmail and iCloud use OAuth and take a few seconds; older IMAP providers may require an app-specific password generated in your account security settings.

2. 2

   Create a folder inside the IMAP account

   Right-click the IMAP account name in the sidebar and choose New Mailbox. Name it something clear, such as 'Archive from Mac'. Folders created inside an IMAP account are stored on the server, not on the machine, so they appear on every connected device immediately.

3. 3

   Drag messages or folders into the IMAP mailbox

   Select the messages or folders you want to move from 'On My Mac' and drag them into the IMAP folder you just created. Apple Mail uploads them to the server as the drag completes. Large folders take time — leave Mail running and your Mac connected to the internet until the activity spinner in the bottom status bar disappears.

4. 4

   Confirm the upload before closing the Mac

   Click the IMAP folder and verify the messages are there. Then log into the provider's web interface — Gmail.com, iCloud.com, Outlook.com — and confirm the folder and its messages appear there too. If they show up on the web, the server has them and the Mac is no longer the only copy.

5. 5

   Open the account on Windows

   Sign in to the same account in Outlook, Thunderbird, or whichever client you use on Windows. The folder and its messages appear in the sidebar as the client syncs down from the server. No import step is required — IMAP handles the delivery.

Method 2: Export to .mbox and convert on Windows#

Use this method when messages live under 'On My Mac' and you cannot or do not want to route them through a server — the account is POP3, upload bandwidth is too slow for a large archive, or you are closing the account entirely and need a clean offline copy. Apple Mail exports messages as .mbox files, a widely supported format that most mail clients can read. The catch: Outlook on Windows does not support .mbox natively, so a conversion step is required if Outlook is your destination. Thunderbird handles .mbox directly with one add-on.

The export itself is straightforward. Most of the friction is on the Windows side, where you need the right tool and import path for your target client.

1. 1

   Export the mailbox from Apple Mail

   In Apple Mail, select the mailbox you want to export in the sidebar. Go to Mailbox > Export Mailbox, choose a destination — the Desktop is easy to find — and click Choose. Apple Mail creates a folder with an .mbox suffix containing the messages as plain text files. Large mailboxes with many attachments can take several minutes. Do not let the Mac sleep during export.

2. 2

   Copy the .mbox folder to your Windows machine

   Move the exported .mbox folder to a USB drive, an external hard drive, or a shared cloud folder accessible on Windows. The .mbox folder is a collection of plain files and transfers without special software. Keep the folder structure intact — do not rename the folder or pull individual files out of it.

3. 3

   Import into Thunderbird using ImportExportTools NG

   If Thunderbird is your Windows client, install the ImportExportTools NG add-on from the Thunderbird Add-on Manager. Once installed, right-click a folder in the Thunderbird sidebar and select ImportExportTools NG > Import mbox file. Navigate to your .mbox folder and confirm. Thunderbird reads the format natively and places messages in that folder without a conversion step.

4. 4

   Convert to .pst and import into Outlook

   If Outlook is your Windows client, convert the .mbox to .pst first. Several desktop utilities handle this — choose one that explicitly states compatibility with the current macOS Mail .mbox structure and Outlook 2016 or later's .pst format. Run the conversion, then open Outlook and go to File > Open and Export > Import/Export > Import from another program or file, select Outlook Data File (.pst), and follow the wizard.

5. 5

   Verify messages and attachments on Windows

   After import, spot-check several threads including ones you know had attachments. Attachments in .mbox files are stored inline as MIME parts. If any are missing, the export was likely interrupted mid-write. Re-export from Apple Mail to a fresh destination and repeat the import.

Which method should you use?#

The right choice depends on where your mail lives and which client you are landing on. The table below maps each situation to the correct path.

What to do when the transfer does not work#

Most failures in this process come from a small number of causes. The ones below cover the majority of cases.

• IMAP upload stalls mid-transfer. Check Mail's activity viewer under Window > Activity to see whether uploads are in progress. A frozen progress bar usually means a dropped connection. Quit and reopen Mail to restart the sync. For very large mailboxes, a wired ethernet connection is more reliable than Wi-Fi for a sustained upload.
• Folder shows on Windows but messages appear empty. This is normally a download cache delay, not a missing message. In Outlook, right-click the folder and choose Update Folder. In Thunderbird, right-click and select Get Messages. Allow a few minutes for the client to pull message bodies from the server.
• .mbox file appears as an unreadable folder on Windows. Windows does not recognise .mbox as a mail format — it looks like a plain folder of text files. That is expected behaviour. Do not try to double-click into it; import it through the mail client's import function as described in Method 2.
• Conversion tool produces a .pst that Outlook rejects. Older utilities sometimes write a .pst in a legacy format that Outlook 2016 and later cannot open. Look for a converter that explicitly lists compatibility with Outlook 2016 or 2019 and the newer .pst format. Running Outlook in compatibility mode does not fix this — the tool needs to write the right format version.
• Attachments missing after .mbox import. Attachments are stored as MIME parts within the message text. If they are absent after import, the export was interrupted before those messages were fully written to disk. Close Apple Mail, reopen it, select the mailbox, and run a fresh export to a new folder on the Desktop.

A faster way to keep email accessible across Mac and Windows#

If you are making this move because you regularly work across both platforms, the IMAP method points to a simpler long-term arrangement: run your mail through a client that works identically on any OS, so the question of transferring files between machines never comes up again.

We build AI Emaily — an AI-native email client that connects to your existing Gmail, Outlook, iCloud, or any IMAP account without migration. Because it runs in the browser and ships a downloadable Windows installer alongside its Mac app, the same inbox, folders, and AI-assisted draft queue are available on both platforms from the same account. There is no file transfer involved because there is no local archive — connect the account, and every device reads from the same server.

AI Emaily runs a 7-day free trial. You can connect your existing account at aiemaily.com, check that all your folders are visible, and decide whether it replaces Apple Mail on your end-to-end workflow before committing.