Set up macOS default Mail.app to use Exchange

You need macOS 10.14 (Mojave) or newer which supports Modern Authentication. 10.13 (High Sierra) or before must be upgraded. Some of the screen examples below may differ depending on the version of macOS.

1. Review your current setting

1. Launch Mail.app. Click “Mail” > “Preferences…”.
   
2. Select “Accounts” from the top icons and find your Primary Mail Address account. If you see “IMAP” or “POP”, you need to follow this instruction to set up your account again. If you see “Exchange”, no action is required.
   

2. Change POP setting (when your account is “POP”)

If your account is “IMAP”, proceed to “3. Export the current account data”.

If your account is “POP”, you may need to change POP setting to avoid deleting messages from the mail server while following this manual. Please also refer to Extra warning about POP.

1. Remove a check from “Remove copy from server after retrieving a message”
   

3. Export the current account data

1. Select a mailbox you want to export from the main Mail window. You may select multiple mailboxes by holding a “Command” key and click folders. Click “Mailbox” > “Export Mailbox…”.
   
2. Choose a folder and click “Select”. The window just closes, but the selected mailboxes will be exported in the background. It may take a while.
   
3. The exported mailbox is stored in a folder named “(mailbox name).mbox”. If you selected multiple mailboxes, a separate folder is created for each mailbox. If the same folder already exists, it is not overwritten and a new folder with a number will be created.
   

4. Add a new account

Turn off the current account and add a new account with Exchange connection.

1. Click “Menu” > “Preferences…”.
   
2. Select an “IMAP” or “POP” account you want to turn off, and remove the check of “Enable this account”. The account will be disappeared from the main Mail window, but this account data is not removed from the application yet.
   
3. Add an Exchange account by referring to the following manual.
   • macOS Mail.app
4. You may use Mail.app as is or remove the old account. Select an account you want to remove, and click “-” (minus sign) at the bottom left.
   
5. When you see a warning pop-up, click “OK”.
   
6. You see a different warning pop-up. Click “OK” again.
   

5. Read the exported old account data file

You can read the exported data file as follows.

1. Click “File” > “Import mailboxes…"
   
2. Select “Apple Mail” and click “Continue”.
   
3. Choose a “.mbox” folder and click “Choose”.
   
4. Click “Done”.
   
5. You can find the imported mailbox in the folder named “Import” under “On My Mac” entry.