OT: still seeing spam

I am still getting several spams a day on this list. As far as I can
see in the header it is not spoofed but actually sent via the list.
Is there anything that can be done about this? Stricter
filtering/matching of membership of senders or something?

Compared to the rest of the spam I get it is not much, but it is
irritating.

Frits

-- 
Frits Kuijlman					    frits@cistron.nl
Delft, The Netherlands