There are several operations that you can perform on a file list in addition to just opening the items in the list. You can either click on the icon or use the menu. If you are in a conference, the message is addressed to the conference automatically. A copy of any new message you create is always placed in your Mailbox. See the Addressing page for more information on addressing and sending messages.
All replies become part of a thread that starts with the first message.
The thread allows you to track all responses to the first message. Next in Thread opens the next message in the thread. Threading also works within your Mailbox. Your can now drag messages into the folder. When you log into the client, you generally want to read our unread messages right away.