Once the spammers have your email address thats it im afraid. When they are fed up of spamming you personally, they will sell on your address for someone else to spam you!
You could try Mailwasher which will allow you to access the mail while it is on the server and those that are spam can be rejected to the spammer and appear as if the address is invalid. They should give up after a while but it may be a long wait.
To prevent spam inthe first place use two email addresses. Most ISP's allow at least two and one you would use solely for sites that you have to register on but really do not wish to have mail sent to you. You would then simply leave this address out of your outlook accounts and so avoid collecting spam.
Also, Never, never, use your email address on newsgroups for replies you make to posts (this site excepted - addresses are server side and need registration to access even the facility to send mail)
I made the big mistake of using one of my real addresses on a Microsoft Newsgroup and have since been asked if I would like to increase my size by three inches so many times that I would now be over twenty feet (I leave it to those who have recieved this sort of spam to explain....)
Spammers use web crawlers to "harvest" addresses from such groups so if you have to use your address then put myname"REMOVE"@ISP.com to make it obvious to any human what is wrong with the address to get mail to you.
Apart from that, there is little to be done.