I made up a new way of blocking spam: MTX records

[darxus]

http://www.chaosreigns.com/mtx/

MTX records are just DNS A records on your DNS server stating that an IP is a legitimate mail transmitter.

There is a SpamAssassin plugin for it on that page.

Comments

[darxus.livejournal.com]

I just added a "Conceptual Origin" section. All about SPF and DNSWL.