[Resending after a botched cut-n-paste]
Keld Jørn Simonsen wrote:
So what information could be used reliably in an enhanced greylisting?
What about the subject, and the date?
Date no, for the same reason as Message-ID; template driven systems
insert the current date on the fly.
Subject should work, since in my experience the only variables included
in the Subject will remain the same on retransmission: customer ID,
campaign ID, list name, that sort of thing. Of course, real MTAs don't
frob the subject at all.
What surprises me most, though, is that gray-listing is working for
anyone. The entire assumption behind gray-listing is that zombies don't
grok 4xx errors. I don't see any evidence of that; what I'm seeing now
is the zombies will slam the same identical message at you three or four
times. Gray listing used to work pretty well for me a year ago, but I'm
pretty much ready to turn it off now, all it does is slow down
legitimate mail.
<csg>