Hi Serge,
You can turn off registration confirmation, but to turn off all email completely would require hacking the code itself. Can I ask you if you're 100% positive you want to do this?
What will prevent somebody from going in and signing up under a number of different bogus email addresses and pretending to be someone other than who they really are? I don't think I'd open myself to that kind of lawsuit if I were you.
Just my 2 cents...