Not for the first time, important correspondence has gone unread/deleted/ignored due to being automatically diverted to my junk mail folder.

Just now I discovered I could have gotten my broken iPod back almost 2 weeks ago and my new headphones delivered one week ago, if I'd simply known about e-mails concerning their respective repair/delivery, which I would have thought would have turned up in my inbox.

Who can I get swift, disgusting revenge on for this? Or at least, how can I designate which mail is actually junk and which mail I need?