Let's highlight the main components of the SiteMail interface.
At the top of the interface, find the primary navigation tabs: Email, Contacts, Calendar and Settings. By default, SiteMail always starts in the Email tab.
Immediately under each tab, a row of contextual sub-menu options appears. These options will change based on the tab you select.
The Inbox and all other folders appear on the left side.
The list of e-mail messages - sortable by sender, subject, date and size - appears in the middle.
The Search entry box and Sign Out link can be found in the upper-right corner of the interface.
Immediately below the Sign Out link, find the 2-pane and 3-pane icons. Above, you see the default 2-pane view. To automatically preview a message's content, click the 3-pane icon, as seen below.
If you prefer the 3-pane view, change it in Settings.