Selecting the Mail Activity icon from the Navigation Panel displays the Mail View, and Mail Toolbar (1) in the activity panel and the Mail Menu actions on the menu Bar.

Mail View with Preview
Depending on the Mail folder selected in the Tree view in the Navigation Panel, the Mail view displays the folder name (2), and the messages stored in the Mail Folder (3). You can display a preview of the message selected in the Mail view by clicking on the Preview Button on the Mail Toolbar or by selecting the View | Preview Message Menu action.
You can increase or reduce the size of the Preview Panel by dragging the divider (5) up or down with the mouse.
The Preview panel provides information on the message From, To, CC, Subject, Sent, Received and Content type fields (6), and it displays the content of the message in the area (7). You can switch between different content types for the message using the RAW, PLAIN, and HTML buttons. The RAW button will display all the contents of the message without formatting or reference to external resources on the internet, and it is useful to view the whole message. The PLAIN button will display the content of the message as plain text, if the message has a plain text content type. The HTML button will display the content of the message as a web page. If you are connected to the internet, and not working offline, the preview panel will download images as required by the message from the internet to display.
Further reading from Mail View: