Either "Newest first" or "Oldest first". Determines the default order of messages in any selected list

The default value for the Display/Tags menu entry. When set to "Yes", a panel with a button for each tag is shown, each button being set when the corresponding tag is assigned to the message currently selected.

Tells what should displayed in the "From" column of message lists: either the name of the sender (when known), or the email address.

when set to Yes, URLs in the body panel appear as clickable links. The browser may need to be configured in the Paths sections.

When a message has both HTML and Text alternative representations, this option indicates which format should be shown first in the message pane. Text is the most secure choice.

When all messages of a list have the Sent status, the Sender column is automatically switched to a Recipient column when this option is set to Yes. The column is switched back automatically to Sender when the list contents change, or manually with the context menu of the columns headers.

The default value for the Display/Threaded menu entry. When set to "Yes", the messages that belong to a same thread are shown in tree-like representation, and the threads can be opened and closed.

How the dates are displayed in the message lists. Choose DD/MM/YYYY HH:MI or YYYY/MM/DD HH:MI depending on what you find the more easy to read.

set to "None" or "System". When a new mail is imported by the server, if set on "System", a notification to the desktop system is issued. This feature works currently on Unix/MacOS X desktops that have a notification interface. On MS-Windows it has no effect.

The Qt library has several builtin styles (the actual list depends on the platform the interface is running on). The style controls the overall look of the interface as well as some usability tips, such as the function of the middle mouse button. Just try different styles and keep the one you like the most.