Don't click on any email with attachment (the paper clip symbol) unless you know who it is from and are expecting it.
And don't answer any of the spam emails, then they know your address is a good one and they will sell it to all their friends.
If you sell anything on Craigslist, beware the answers that ask "Is this still available?" without saying what it is. They, too, are collecting email addresses to add to their lists. I always disable email answers on CL, if they really want it, they can call my (anonymous) Google Voice phone number.