How to Set Up “Mail Days to Sync” in e-mail (iPhone/iPad)
By default your iPad/iPhone is set up to sync 1 week of mail. This means you can only see mail you received in the last week in your inbox or any of your e-mail folders. You will want to change this setting. We recommend you use the maximum setting of "No Limit" so that you can see as many messages as possible in your inbox and folders. This process is shown using iOS 8.