How do I change settings for the preview pane in Mail?
You can show or hide the preview pane, and you can display it on the bottom or the side.

How do I mark all previewed emails as read?
You can mark all messages you view in the preview pane as read.

How do I view emails as conversations?
You can view a message grouped with all of its replies so that you can read the message and replies all at one time. A message grouped with all of its replies is called a conversation and conversations save you the trouble of looking through your Inbox to find individual replies.

How do I change who is added to the type-ahead list?
The addresses that appear in the type-ahead list are chosen automatically, based on the people with whom you recently emailed, chatted, and had meetings. You can change whether or not CC and BCC recipients are added to the type-head list, or whether to add names from all emails or just from emails you send. You can also choose to stop adding any names to the type-ahead list.

How do I set a default font for mail?
You can set a default font for mail that you send.