How to fix macOS Mail app failing to authenticate with Office 365 after changing your Microsoft 365 password

Summary

This guide helps you troubleshoot and resolve: How to fix macOS Mail app failing to authenticate with Office 365 after changing your Microsoft 365 password. Follow the steps below to fix the issue.

Common Causes

If you have recently changed your Microsoft 365 password, the macOS Mail app may stop authenticating your account. This usually happens because the app is still attempting to sign in using your previous credentials. This guide will help Brisbane small business users clear stored passwords and reconnect their Microsoft 365 email account to macOS Mail.

Quick Fix Steps

1. Quit the Mail app completely.
2. Open Keychain Access and delete the cached Microsoft 365 password.
3. Remove the Microsoft 365 account from Mail Settings.
4. Re-add your Microsoft 365 account using your new password.

Detailed Instructions

Step 1: Clear the cached password from Keychain Access

1. Close the Mail app if it is currently open.
2. Press Command + Space to open Spotlight Search.
3. Type Keychain Access and press Return.
4. In the search bar at the top right, type your Microsoft 365 email address.
5. Locate the entries related to your Microsoft 365 email address.
6. Right-click the entry and select Delete.
7. Confirm the deletion when prompted.

Step 2: Remove the account from macOS Mail

1. Open the Mail app.
2. In the top menu bar, click Mail and select Settings (or Preferences on older macOS versions).
3. Click the Accounts tab.
4. Select your Microsoft 365 account from the list on the left.
5. Click the - (minus) button at the bottom of the window to remove the account.
6. Click OK to confirm.

Note: Removing the account from Mail will not delete your emails from the Microsoft 365 server; it only removes the local configuration from your Mac.

Step 3: Re-add your Microsoft 365 account

1. With Mail open, click Mail in the top menu bar and select Add Account.
2. Select Microsoft Exchange from the list of providers.
3. Enter your full Microsoft 365 email address and click Continue.
4. When prompted, enter your new Microsoft 365 password.
5. Follow the on-screen prompts to complete the authentication.
6. Select which apps you want to use with this account (e.g., Mail, Contacts, Calendars) and click Done.

Troubleshooting

Authentication loop or repeated password prompts

• Ensure you have a stable internet connection.
• Restart your Mac and repeat the steps above.
• Check if Multi-Factor Authentication (MFA) is enabled on your account. If so, you may need to create an App Password in your Microsoft account security settings.

Mail app fails to sync after reconnecting

• Go to Mail > Settings > Accounts.
• Select your account and ensure Enable this account is checked.
• Click Mailbox in the top menu and select Get All New Mail.

Note: If you use Outlook for Mac instead of the default Mail app, the process is similar: go to Outlook > Settings > Accounts to remove and re-add your profile.

If you continue to experience authentication errors after following these steps, please Open a Ticket with our support team.

Still Having Issues?