I hate spam myself and I don't sell your email address, ever.
Having said that - all the three fields are necessary.
If you still consider your email address is still too precious (or if you don't believe me enough) - then just fake an email address. Of course in that case I won't be able to contact you back.
- I need your name to identify you.
- I need your email to contact you back.
- And of course I need your message to know what you want to tell me.