Re: [Full-disclosure] throwing the book at spam



On Sun, 16 Jul 2006 11:33:32 BST, lsi said:

These tests are fairly self-explanatory, with the exception of the
analyse_received test. This test analyses the significant Received:
headerline inside each mail (there are usually several Received:
lines, but only one is relevant for our purpose). Any mail with an
invalid Received: line is deleted. The tests for validity are as
follows:

IP_missing
IP_obfuscation
IP_unreversible
by-line_not_present
sending_SMTP_server_unresolvable
sending_hostname_not_provided

Note that these tests are *very* hard to get right. In particular, they
tend to fail spectacularly if you don't allow for the fact that many times,
the mail originates inside an RFC1918 private network, so trying to resolve
the IP addresses will fail.

There's also a lot of other ways this can bork up if at any time a split-view
DNS was involved, or there is/was a temporary DNS outage....

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