as un-geeky as possible, the 'sender' of spam almost never resolves to an actual email address. they spoof them, mask them, do everything possible to make them untracable.
i get emails that appear to be coming from my domain but arent. i get emails that appear to be sent to me, but in the properties of the message reveal they are supposed to be going to some other addy but my name is put there instead.
never open spam mail. if you use outlook express, you are pretty much doomed as it 'previews' messages and i have not found a way yet to disable that feature.
i use the regular outlook, and have 'preview' turned off. any messages taht i cannot tell by looking at the subject or from are spam, i right click, and choose 'options'. i can see the nitty gritty of it and find out if its actually work related and safe to open.
i get at least 100 messages every day that go straight to my trashbin.