[lug] Filtering mail sent to root

[Bill Thoen]

A lot of annoying spam comes to my root account, and currently I just send
it to /dev/null, but then I got to thinking that it might be good to
accept mail generated by any process on my machine (usually these are
alerts that something somewhere has come unglued.)

So what's the best way to dump any mail that originated from outside the
box, but keep the internal messages?

- Bill Thoen