Built into Outlook is a Spam filter that can work very well. the trick is to teach the filter which emails are bad and which are not, and that's great for individual emails, but the spammers will use 1 domain and then vary each address so they keep coming thru as a new email. what i've done is edited the emails that i entered as spam to keep out the entire domain, not just 1 email, all from a domain. i've built this list for over a year so it'll help keep a lot of spam out.
Download the Spam domain list Here, Import directions below
If you want to learn more about the spam filter, check out this Outlook Spam Filter Tutorial provided by sitedeveloper.ws