From Contact Plus Corporation:
Spam Buster requires a POP3 email account such as provided from a local internet service provider and does not support proprietary email such as AOL , CompuServe, MSN, Juno, or web-based mail accounts such as Yahoo or Hotmail. To use Spam Buster you customize the filters for selecting exactly which emails you want deleted. Based upon your filters you can keep get rich quick schemes and pornographic email out of your email box. It's easy to add new filters to the list to keep out the ever growing realm of junk email. Plus Spam Buster comes with a list of over 17,000 known spammers. Spam Buster uses DNS lookup to validate the domain name portion of the email address. Spam Buster scans up to 12 unique email accounts and can run in the background through the system tray, checking your email periodically for new messages every so many minutes. Spam Buster even provides comprehensive statistics and charts of how often you're getting spammed.