I have had good results using
SpamSieve. With proper
training it is adept at detecting the kind of spam you are getting.
My experience so far is less than good. SpamSieve provides instructions of epic proportions so I figured "step by step" and "exactly what they say" would be best and that's what I did. However, I got to a point where SpamSieve highlighted a pile of my real mail, by greying it out.
At that point, I worried that I could be executing a command that deletes a bunch of mail I want, so I decided to stop everything. I removed the SpamSieve extension and, according to their Uninstall instructions, moved SpamSieve to the trash. However, my mail remained greyed out, so I did a restart.
However, all the same mail remains greyed out. Any thoughts on how to fix that?
Edit: I fixed it. All the greyed out messages had a bar across the top saying I had labeled it as Junk, so I went through the messages, one by one, and checked off "Not Junk". No more grey.