[exim] Iptables/other blocking ylmf-pc clients

Hi All

Its easy enough to add a rule to the exim config to always reject
connections which HELO ylmf-pc. However they still seem to hammer away.

Has anyone come up with anything slick to block the ip address of
clients that make a ylmf-pc request?

Log tailing would be ok, but it seems that an external program could
fairly easily be called (denyhosts or similar)

Dean