Mary Morris writes:
> Can anyone see a reason to not use firewall techniques to refuse
> a connection to port 25 from specific systems or domains? By refusing
> connection to a known email transit point, email can be denied
> without ever receiving it to examine it. This of course does nothing
> to the good domain with one bad user. I use a piece of software
> called TCPD which refuses connection to any host in a hosts.deny
> file for services.
The problem here is that the spam source can simply direct the mail via
an innocent third-party system, which will (most-likely) accept it and
then forward it to you. The TCP connection will then be from a
different host than the one you are blocking.