It’s an MDA, written in python with a filtering mechanism using white lists (the e-mail addresses you trust), blacklists (the spammer mail addresses). Additionally, e-mails use a tagging mechanism like time-dependant addresses or for a certain kind of communication. The cool thing though, e-mail addresses which are neither in the white- nor in the blacklist need to be confirmed by the sender. I’m actually a bit curious how this will work.
If you’re bombed with spam each day, you may want to have a look at TMDA. Though you should know how to setup your mail queue, it’s not as easy as installing Mozilla Thunderbird on your system.