Its a toughie.
Best thing is to have a "throw down" email account for everything you have to list an email addy for - like a free hotmail account.
And as mentioned above keep your "real" email account close to the vest.
Also, I don't use Outlook or Outlook Express. Just don't use them. I currently use the free Mozilla Thunderbird, which is pretty good, with its own anti-spam thingy built in.