Internet security dilemma?

My field of business requires me to stay a of financial markets and being a member of several internet forums is a must. There is a forum I am getting ready to join, but I am hesitant. I personally know a few dozen people on it, some members are anonymous, some not. My worry is that one of the moderators is one of those “secret agent” types who tries to dig up as much info on members as he can. He also happens to be very computer savvy. He’s basically harmless, but pulls embarring tricks on members sometimes, ie. Signing them up as members for controversial political groups, dating clubs, etc. I want to join that forum, but not have that jerk being able to know who joined or read my mail. What is the best web based email group to use? I've been told yahoo is probably the best. I know I will leave my IP, ISP or whatever that is, but would like to keep that guy from reading all my mail. Any suggestions?