When e-mail authentication is enabled, registering fails with the error: "Passwords are different or password is empty."
The user is created normally, but the 'e-mail verification' e-mail is not send, so the created user is not able to log in. When tried, a notification appears:
"Your account is not yet active, because your email has not yet been confirmed."
My guess is that the system works fine but the error description is misleading people. As a consequence they try to register over and over again, creating a lot of unwanted users.
The error description should say something like:
"Configuration error: Email configuration is not properly set, please contact the admistrator with this notificaton."