In message <20040222131528.GK11328@phaeton.entropie.net>, Martin Weber writes:
>I.e. lock out anyone with a private network who happened to name
>her machines as she liked, and didn't have the money to buy a
>global name? This sounds microsoftish :) (Or those who happened
>to name their private network, but were not quick enough to buy
>the domain, and thus their name is resolvable yet points to another
>IP, like in my case [entropie.net])

No problem.  HELO as your real address.

>Sorry, but this brutal scalpel method doesn't really help us.

Yes, it does.  There is no sysadmin incapable of providing valid reverse
DNS, and this simple filter gets rid of a very large quantity of spam.

-s