Is there any way to allow shared-server customers to send email, even allow them to send the same email to many email addresses, but PREVENT them sending unsolicited email.

I am not talking about relaying email, but allowing them to send email from (perl/php/etc.) scripts.

I am sure the answer is no since there is no way to ascertain if an email is ok or unsolicited, but I am curious as to whether anyone has any suggestions to tis common problem?

Use secure sendmail scripts

or enforce them at least :)

I guess there is no reason why I can't have T&Cs that state that the customer must ensure security of their scripts against relaying email but this wouldn't stop those people who specifically sign up with the intention of sendign spam for a few days and then charging back their credit-card order (or leaving a fraudulant credit-card orcer).