Hi,FWIW: the way I solved it was limiting the number of concurrently incoming spam because my box serves only few different domains, so I limited the number of connections from the same smtp client to 5 using iptables (the connn-limit module). This might or not be possible for others.
This stopped dead "spam outbursts": your 8000 mails per day are NOT received in a linear way, but everytime a spammer sends you a "batch" and you just can not keep up: who would drink from a fire hose ?
HTH JGA
