Re: throwing the book at spam

[Valdis.Kletnieks () vt edu]

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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