LuKreme wrote:
So it looks like the only usefulness of DKIM for spam checking is really for the big mailers like gmail, paypal, ebay, etc?
A pass on DKIM (or any other sender verification system ) is useful for any mailer that you *recognize*, regardless of size.
Trivial example: If you regularly do business with SmallCorp, and you know they sign their mail using DKIM, you can whitelist those messages that claim to be them and come through with a verified DKIM signature.
Successful sender verification ALONE doesn't tell you much, because it doesn't distinguish between a legit sender who uses DKIM and a spammer who uses DKIM (or a spammer abusing a large sender). This is why the default scores on DKIM_VERIFIED and DKIM_SIGNED are just enough to track the rule, and not enough to significantly affect the score
Combine it with a reputation system for those domains, even one as simple as a bunch of whitelist_from_dkim rules in your local.cf, and it becomes a powerful whitelisting & blacklisting tool.
-- Kelson Vibber SpeedGate Communications <www.speed.net>
