SPAMfighter Standard is free to use if you are a home user. If you want to use SPAMfighter in a professional/educational/governmental environment, you must use SPAMfighter Pro.
SPAMfighter Standard will insert a footer/signature in all your outgoing emails with a message that your mail is protected by SPAMfighter. In your Outlook interface there will also be a small text message/commercial. With SPAMfighter Pro you will also have access to premium support, allowing for faster response times to your questions. Finally, only with SPAMfighter Pro you will be able to have more than 100 people in your Blacklist/Whitelist.
You can see the full list of differences here, where you also buy SPAMfighter PRO.
