There's a user in my office who has access to a shared mailbox. It's only showing messages from the last 3 months, which I know how to change, by going into account settings. But when I look in Account Settings under Email Accounts, all I see is the one under his name. The shared mailbox is not there. But when I try to add it, it tells me he already has it. Why isn't the shared mailbox showing up under his email accounts? Is there some way I can change the settings even if it's not there?