How to fix macOS Mail app failing to sync emails with Microsoft 365 Exchange

Summary

This guide helps you troubleshoot and resolve: How to fix macOS Mail app failing to sync emails with Microsoft 365 Exchange. Follow the steps below to fix the issue.

Common Causes

This guide provides steps to resolve sync, send, and receive issues with Microsoft 365 Exchange accounts in the macOS Mail app. These issues are often caused by outdated account credentials, network connectivity problems, or corrupted mail profiles.

Quick Fix Steps

1. Restart your Mac to clear temporary system glitches.
2. Check your internet connection by opening a website in Safari.
3. Quit the Mail app completely (Command + Q) and reopen it.
4. Check the Microsoft 365 service status to ensure there are no outages.

Detailed Instructions

Verify Account Credentials

If you recently changed your Microsoft 365 password, Mail will stop syncing until the new credentials are saved.

1. Open the Mail app.
2. From the top menu bar, click Mail, then select Settings.
3. Click the Accounts tab.
4. Select your Microsoft 365 Exchange account from the left sidebar.
5. Update your password in the relevant field if prompted or if it appears incorrect.
6. Close the Settings window and allow Mail to synchronise.

Check Mailbox Behaviours

Incorrect folder mapping can make it appear that emails are missing or not syncing correctly.

1. Open Mail Settings and go to the Accounts tab.
2. Select your Exchange account.
3. Click the Mailbox Behaviours tab.
4. Ensure that the Drafts, Sent, Junk, and Trash folders are mapped to the corresponding server folders rather than "On My Mac".

Troubleshooting

Remove and Re-add the Exchange Account

If sync issues persist, removing and re-adding the account often forces a fresh synchronisation with the Microsoft 365 servers.

1. Open Mail Settings and click Accounts.
2. Select your Microsoft 365 account from the list.
3. Click the minus (-) button at the bottom of the window to remove the account.
4. Click the plus (+) button to add a new account.
5. Select Microsoft Exchange and enter your full email address.
6. Follow the on-screen prompts to sign in and grant the necessary permissions.

Check macOS Internet Accounts

macOS manages Exchange accounts through system-wide Internet Accounts settings. Conflicts here can affect the Mail app.

1. Click the Apple menu (Apple icon) and select System Settings.
2. Scroll down and click Internet Accounts.
3. Select your Exchange account and ensure that the Mail toggle is switched on.
4. If the account is listed but not working, remove it from here and re-add it via the Mail app.

Still Having Issues?