Opening a shared mailbox for mobile devices is a new Office 365 feature available since September 2019. The following steps are only supported in the latest release of the Outlook app for iOS and Android.
- Ensure that you have your primary mailbox already registered with the Outlook mobile app before proceeding to add the Shared Mailbox.
- After the primary mailbox is added into the Outlook mobile app, tap the Add Mailbox icon again on the left navigation bar to add a Shared Mailbox.
- Choose the Shared Mailbox option from the menu.
- Select the primary mailbox that is delegated permissions to open the Shared Mailbox you wish to link/register.
- Enter the email address of the Shared Mailbox.
