http://www.postfix.org/SASL_README.html You might trim $my_networks to NULLYou might configure something like amavis/clamav to virus check your mail. (though this will do nothing for your SPAM)
You might get agressive about checking your logs and assist your users in virus removal, or use something like iptables to deny access to all infected IP#
########## Adrian Minta wrote:
I need an advice on the following problem:I setup an email server for a small ISP. The server is sarge with postfix as MTA. Unfortunately some of the clients contacted a virus/spambot that is sending spam via my mail server. I want to bloc spam that came from $mynetworks but the sender in not in $relay_domains. Is such thing possible ?Thank you in advance !