spamhaus
In September I had the pleasure of being a Twitter panelist on how to avoid the spam filters when emailing. This is the third time I've spoken formally on the subject (if you consider tweeting "formal"). By this third presentation, it struck me that spam is like porn, everyone thinks they know it when they see it, but few can define it in their own words. Looking for the most succinct explanation, I turned to the Spamhaus Project