The mailer don’t send password to new users to comment

I’d installed wordpress and everything is right, but the fact that when a person registers to receive a password by email, it is not sent. I, as the admin, receive the email notification of new user, but the user don’t receives his password on his e-mail. The option “Anyone can register” and “Users must be registered and logged in to comment ” on admin>options>general are allowed. As well as the option “Allow people to post comments on the article” on admin>options>discussion is activated. Will I have to restore some file? Someone can help-me? Thanks by attention on this.