The Inbox Tab shows you all of the outside image(s) of your mail. 

You can sort your mail items in your inbox by Clicking the "Show" drop-down box to view Open Requests, Scanned Items, Letters & Large Envelopes, Packages & Letter Packs, or Stored Items.

You can also sort your mail items by the date received. Click on the "Sort By" drop-down box to choose the earliest or the latest items.

To make a request for your mail to be processed, you can select your mail items and choose from the menu options in the Top Toolbar.