Two lines of defense in its mail client:

1) Message filter: easy to use, but not very bright (when will someone implement a message filter with Boolean logic (AND, OR, AND NOT, NEAR) and/or regular expressions?)

2) Span Idenitifier: Automatically teaches itself what constitutes SPAM. I get approx. 500 Spams a week, and this thing pegs about 90% of it. You have to teach it what's SPAM and what's not, but after a while, it gets pretty good.