We will reformulate that. What we mean is that we never save user emails on our servers in clear text. The emails are encrypted on the clients before being sent to us. We want to know as little as possible about our users.
okay, so you can easily make a rainbow-table and thus your users are not anonymous anymore + if someone has your database and want to know if email@email.com has an account one can easily find that out, even without the need to bruteforce all emails. Btw. in this case it makes absolutely no difference if you or the client computes the hash ;)