Spam Killer
I find POPFile to be very effective at throwing spam into my Deleted Mail folder. It was 99% correct for the month of November on about 1750 emails, 75% of them spam.
You have to train it, however, and continue to train it when it makes a mistake. That takes five minutes every few days since it makes so few mistakes. My experience was about 75% correct after a couple of days, and improving after that. Probably 90% at the end of a week.
POPFile is free, but the author asks for a contribution. I gave. I use version 0.18.1, which is much smaller than the latest version and works file for me.
SC