Anonymous can't send mail to user

When i'm not loggued, i go to ...user//contact
and have a "you have to set your email in your account at user/0" msg.
Maybe when anon email try to send email you could display the contact form and add a "from" field specially for the anon user to put his email then check if a "from" field is POSTed, that the anon email is regex mail pattern friendly, and set it as sender adress instead of user/0 email.

Thanks