Exchange Intelligent Message Filter. This will filter e-mail at the Exchange Server; however, it is more efficient to do so before message enter the environment such as by using a hosted message filtering solution like Microsoft Exchange Hosted Filtering.
This question/answer was about Lotus Notes but the same holds true for Exchange. That is the nice thing about a vendor-neutral solution. Getting this traffic off of your network is definitely a cost savings to you and your users.
Have you ever heard of SpamBayes? This can be deployed on a workstation, it is Python based, and it is very good at catching spam.
Hope this helps!
Any antivirus or anti-spam software are effective in eliminating malicious software as they are designed to scan and quarantine potential risks on your computer. However, you have to keep in mind that they are effective when they are installed with full license. You have to use a licensed antivirus software.