To add access to shared mailbox
Classic Outlook (Windows):
- File → Account Settings → Account Settings
- Select the user’s Microsoft 365 account → Change
- Click More Settings
- Go to the Advanced tab
- Under Open these additional mailboxes, click Add
- Type the shared mailbox or user’s name
- Click OK → Next → Finish
- Restart Outlook
New Outlook for Windows:
- Click your profile picture in the upper-right.
- Select Add shared mailbox.
- Enter the mailbox name or email address.
- Click Add.
Outlook on the Web (OWA):
- Right-click Folders in the left pane.
- Choose Add shared folder or mailbox.
- Search for the mailbox.
- Click Add.