So I went ahead and put Project Spamhaus into my mail server.
What they do is keep a list of known IP addresses of machines that spam. So every time I get an email from someone, it checks this database and see if it's a known spammer. If it is, my mail server will block it.
There's several of these projects going on, another one is The Open Relay Database.
Anyway, I've just turned it on and (not more then 5 minutes) and it's already blocked 2 emails. Hopefully they are spam and not email that I should be getting. :>
This is in no way perfect, 5 spam emails also came through, but my Cosplay.com notifications came through too so... I'll let it run for a few days and see how it goes.
I'm also wondering if this will get bypassed, because I have my ISP secondary my mail server. So if my connection goes away or my machine is down for some reason, they queue up my mail until my mail server comes back up.
Will spamming software get around my DNSBL by sending the mail to the mail secondaries? Will my mail server still check when spam is coming from a mail secondary? I'll check the logs after a few days and see I guess.
Anyone else have experience using DNSBLs? Are there instances when it blocks legitimate email? The documentation says it will happen, but it's rare.
So why the sudden interest? Well we all know spam is annoying, but when a group of anonymous spammers actually get together to sue SpamHaus, you know they are doing something right. ;-)