Move Messages via Drag and Drop in Mac OS X Mail

In Mac OS X Mail, transferring messages is easy, and it is where it shows you're using a Mac:

• Highlight one or more messages in Mac OS X Mail.
• Click and drag the message(s) while holding down the mouse button to any destination mailbox in the mailboxes pane.
• Release the mouse button to drop the message(s) there.

So far, so good and well-known. But what happens when the mailboxes pane is not open?

As soon as you start dragging messages around, Mac OS X Mail will automatically show it. When your drag and drop action has finished, Mac OS X Mail hides the mailboxes pane again.