SEEING MULTIPLE MAILBOXES IN THE SAME WINDOW

If you want to see the contents of multiple mailboxes displayed in the same window, just click on the first mailbox you want to see (they're nested under your Inbox), then Command-click on the second mailbox, and you'll get a merged list in the main window. This is really handy for things like looking for an important incoming email when you have multiple email accounts. By Command-clicking on the different accounts, you can see all your new mail, from all your accounts, in one window at the same time. Think about it. It boggles the mail. Uh…the mind.