Published at LXer:
Admins, as a general rule, spend far too much time and energy trying to keep spam out of the networks. Until technology is developed to reach out and touch spammers — forcefully — spam will be an unfortunate and expensive fact of life. Fortunately, some simple hacks can be applied at the server level to derail a significant amount of spam. For Postfix admins, for example, there is the Postgrey Greylisting Policy Server.