- In Microsoft 365 Outlook, click “File” on top
- Type “Control Panel” in search box and then select the best match result “Control Panel” App
- Outlook will search for accounts. Click “Advanced options”
- “Tick” the box of Let me set up my account manually. Then enter the UID of the mailbox needs to be added in Email address field and then click “Connect” button
- Select and click “Microsoft 365” icon
- Outlook account configuration in process
- Enter the PIN of the mailbox that needs to be added. Click “Sign in” button
- It will go through MFA to approve sign in request
- Enter the number in your Microsoft Authenticator. Click “Yes” button
- Click “No, this app only” in this screen. The reason is you only need the additional mailbox to be used on Microsoft 365 Outlook rather than other M365 apps.
- Outlook account configuration in process
- Choose the period to Download email for the past for Outlook offline settings. Click “Next” button
- Click “Done” button to finish setup
- After Outlook restart, the left panel will show the other mailbox being added into your Microsoft 365 Outlook
