There's an annoying spammer (that's redundant, isn't it?) who keeps sending me email claiming I'm a big winner in, well, I'm not sure in what, because at that point I stop reading and send the mail to my spam mailbox.
Screen shot courtesy of Coyote Moon, Inc.
For some reason, my spam filter keeps letting the mail come through to my inbox, even when I mark a day's worth of the messages as junk mail.
The messages appear to come from different email addresses, but the same name always appears in the From field, which means I can use Mail's Rules engine to set up a rule that will automatically send the offending messages to the junk mail folder. I'll never know what I might have won, but I won't have to waste any more time manually moving the messages around.
Automating routine email tasks is one of the basic uses for rules. In addition to using rules to deal with spam, you can also set up rules to automatically file much of your incoming mail in designated mailboxes.
To learn more about using Rules in Apple Mail, take a look at Set Up Apple Mail Rules.