Accessing a Microsoft 365 shared mailbox from main email applications like Outlook, Apple Mail, or mobile apps depends on the platform you’re using. Here’s a breakdown for the most common ones:

✅ Outlook for Windows or Mac (Desktop App)

Automatic Access (if you’re granted full access)

  1. Open Outlook.
  2. The shared mailbox should appear automatically in your folder pane.
    • If not, restart Outlook.

Manual Add (if it doesn’t show up)

  1. Go to File > Account Settings > Account Settings.
  2. Select your account and click Change.
  3. Click More Settings > Advanced tab.
  4. Under Open these additional mailboxes, click Add.
  5. Type the name of the shared mailbox and click OK.

✅ Outlook on the Web (OWA)

  1. Go to https://outlook.office.com .
  2. Sign in with your main account.
  3. In the left pane, right-click Folders > Add shared folder.
  4. Enter the shared mailbox name or email address.
  5. Click Add.

✅ Outlook Mobile App (iOS/Android)

Shared mailboxes cannot be added directly like a normal account. Instead:

  1. Open the Outlook app.
  2. Tap your profile icon > Settings.
  3. Tap your main account > Add Shared Mailbox.
  4. Enter the shared mailbox address.

✅ Apple Mail (macOS/iOS)

Apple Mail doesn’t support shared mailboxes natively. You can:

  • Add it as a separate account (if you have login credentials).
  • Or use Outlook for Mac for full shared mailbox support.

✅ Other IMAP Clients (e.g., Thunderbird)

Shared mailboxes are not directly supported unless:

  • You have login credentials for the shared mailbox.
  • Or you use a workaround like delegated access via IMAP, which is complex and not always reliable.