[Mailman-Users] how to delete spam?

[Gabor Zalavary]

hi,
I've got a list and I would like to drop (delete) all mails which are spam:-)
more precisely I'd like to delete all incoming mails which to: or cc: field
doesn't contains the address of the list. currently all such mails goes under
"Tend to pending administrative requests" and the administrator have to
delete these mails. 
so my questions: how can I delete these mails? is there any options for this?
thanks in advance.