If an administrator has granted you ‘Full Access’ permissions to a shared mailbox, Outlook often detects this permission and adds the shared mailbox to your folder list within a few minutes, or after you restart Outlook. In the ‘Add shared folder’ dialog box, type the name or email address of the shared mailbox you want to add. In the Outlook mobile app, after you’ve added your primary account, you can usually add the shared mailbox by going to ‘Add Mailbox’ and selecting ‘Add Shared Mailbox’ or by manually adding it using the shared mailbox’s credentials (which are typically your own personal credentials that have been granted access). In the Outlook mobile app, after you’ve added your primary account, you can usually add the shared mailbox by going to ‘Add Mailbox’ and selecting ‘Add Shared Mailbox’ or by manually adding it using the shared mailbox’s credentials (which are typically your own personal credentials that have been granted access). To add a shared mailbox in Outlook, go to your account settings, select 'Add Account', and enter the shared mailbox email address.