Spamihilator 0.9.9.38 is a free antispam filter for your email accounts.
It´s basically a mail server put between your provider´s mail server and your email client, that scans every incoming message, filtering out that ones meeting some built-in criteria (only images, too many addresses, words like viagra, cialis, etc.). It uses the DCC (Distributed Checksum Clearinghouse) to recognize bulk mail. You can get more details about DCC at http://www.rhyolite.com/anti-spam/dcc/.
Installing Spamihilator 0.9.9.38 is easy. It has a wizard that will help you in the process. You´ll have to specify which POP3 accounts you want to include (Hotmail accounts are not included), choose the filters that you wish to use, and you´re ready to go.
Every time you check your emails, Spamihilator will scan them on the fly. You will get in your inbox the ones that passed the scanning, while the rest will remain in its "Training Area". There, you will be able to decide what to do with them. You can mark them as "Spam", "Not Spam" or even mark the sender´s address as a "Friend" to receive every mail coming from that address. When you click over "Learn!", your setting will be applied and remembered in the future.
Every message marked as "No Spam" will be put in your inbox the next time you check your email. The ones marked as "Spam" will remain in the "Recycle Bin". You will still be able to recover them, or delete them permantently.